There is a growing realisation from the Australian government that new models of health care will need to be developed to address the disparity of access, increasing demand and escalating cost of traditional means of delivering health care. There is growing evidence showing health care services can be delivered safely and efficiently by email. Despite this body of evidence the clinical utility of email is occurring at a much slower rate than in other business areas. Technological barriers and privacy risks are often cited as cause of the fragmented adoption and utilisation of email-based telemedicine. In addressing these impediments, the service-delivery application needs to be considered. The service-delivery applications used in email-based telemedicine can be divided into two distinct categories. The first is ordinary email applications — such as the commercial products used for personal communication — and the second is where the health care provider undertakes the development of an email application purpose-written to support their telemedicine service. This aim of this research was to develop a decision support model (DSM) to address the complex issues in choosing the service-delivery application most appropriate for an email service. Three areas which would influence a provider’s decision were identified — i) privacy and security ii) economics and ii) quality of service — and investigated. Most emails are sent in plain text across the Internet and pose a privacy risk. Encryption of the email message is used to mitigate the risk. Two means of encryption were investigated: public key infrastructure (PKI) used in conjunction with ordinary email and secure web-mail applications, which require the development of a purpose-written application. Decisive factors in choosing the most appropriate privacy-enhancing technology for an email-based service were identified by a number of means including: technical assessment of encryption models, literature review, survey of users of an email-based telemedicine service and analysis of client applications used in a telemedicine service. This investigation established that correspondent’s perception to privacy risk, email client application support of PKI, risk tolerance to human error and the technical skill are decisive factors in choosing privacy-enhancing technology. The survey respondents considered a privacy breach during email communication was either likely or very unlikely regardless of whether the communication was encrypted or not. Indicating correspondents are unlikely to comply with encryption especially if the technology is cumbersome. Although the population was of a limited demographic, there was a large proliferation (around 87%) of web-mail clients — for example, Hotmail and Gmail — amongst the users of email-based telemedicine services. Web-mail clients cannot be secured with PKI. Hence, assessment of client-email applications used by correspondents in telemedicine will influence the type of privacy-enhancing technology. Technical assessment of privacy-enhancing technology has identified human-error as a risk when using PKI. Secure web-mail obviates human-error. Therefore, tolerance to human-error risk will be decisive in choice of privacy-enhancing technology. PKI has received criticism for being user-unfriendly and requiring technical proficiency to use. This investigation has established the usability of secure web-mail is comparable to ordinary, unencrypted email. Indicating secure communication is feasible when services are not supported by technical expertise. The cost of providing an email-based service is influenced by the service-delivery application. To develop a purpose-written application will cost the heath care provider but staff may be able to work more efficiently because the resultant application contains telemedicine specific functionality that meet the exact requirements of the service. Staff resources to run an email-based telemedicine service using ordinary email were compared to staff resources to run the same service using a purpose-written application. The purpose-written application afforded a reduction of 3% in time for clinical staff. Ancillary staff savings were more pronounced with a 33% reduction in administrative staff time and a 21% reduction in supervisory staff time. A cost-minimisation analysis established at a workload of up to 5000 email consultations per annum it is more economical to the run the service with ordinary email. For higher workload volumes it is cheaper to run the service with a purpose-written application. The threshold of 5000 emails consultations is the point at which the higher initial development cost of a purpose- written application are offset by staff efficiencies. A sensitivity analysis established the most influential factor in the economic model was workload volume — development costs and variable costs had little influence on the threshold. Response time was established as a quality of service metric after investigation demonstrated increases in response time were strongly correlated with a decrease in utilisation rate. The response time to maximise the utilisation rate was 32h or less. Pre- and post- studies demonstrated a purpose-written application can reduce response times. Telemedicine specific functionality in a purpose-written application was also investigated. Conditions for a purpose-written application — for example, use of multi-disciplinary staff, a priority service model and continuum of care over multiple email exchanges — to be efficacious at reducing response times were established. The conditions identified in the privacy and security, economic and quality of service investigation were amalgamated into a DSM. The DSM was retrospectively tested by comparing the output of the model to a gold-standard of the actual service-delivery used by a number of subject organisations. When used to identify services that required a purpose-written application the DSM was 92% sensitive and 92% specific. The model was also tested prospectively and demonstrated 85% concordance from testers in the choosing the service-delivery application. Testing the DSM identified strengths for both ordinary email and purpose-written applications under different circumstances — indicating both are valid alternatives for email-based telemedicine. The individual requirements of a telemedicine service — for example, privacy requirements, participants, the workload volume, number of staff disciplines, mode of service — will dictate the choice of the most appropriate service-delivery application. Informed decision on when and why to use a service-delivery application has implications for the successful delivery of email-based telemedicine services because the choice of service-delivery application will affect: - The staff resources needed to run the service; - The capital cost of implementing a service; - The operating costs of running a service; - The response times to client emails which in turn, influences the utilisation of the service; - The privacy-enhancing technology which in turn, influences the usability and compliance to legislative and statutory requirements.