Problems associated with the inefficient or ineffective use of medicines at the interface between primary and secondary health care are well recognised and remain largely unresolved. Attempts to resolve difficulties at the interface have, to date, focused on national guidance with a view to improving communication between health care professionals. The research presented in this thesis examines the root causes of problems with the management of medicines with a view to reappraise traditional definitions of the interface and to learn of the perspectives of the main stakeholders - community phannacists, hospital phannacists, general medical practitioners and hospital medical consultants. The objectives of the research were: 1. To describe and categorise problems relating to the care transfer process that lead to a deterioration in medicines management, 2. To critically appraise the local interpretation and implementation of health policy, 3. To describe staff communication and decision-making processes and 4. To explore reasons why guidance is not put into practice. The research was conducted in a district general hospital whilst the researcher was employed as an Interface Phannacist. Qualitative methods of data collection were deployed as follows. First, 87 case study examples of interface issues were collected from reports made by doctors and phannacists in primary and secondary care and those identified by the researcher. A root cause analysis of each case showed how deficiencies in medicines management processes could contribute to problems and difficulties. The medicines management processes relevant when patients are transferred between primary and secondary care, together with the root causes of interface issues were mapped. The next stage ofthe research involved conducting focus group and semi-structured interviews with seven community phannacists, sixteen hospital pharmacists, nine general practitioners and two hospital medical consultants. Content analysis, based on qualitative research theory, showed participants' perspectives of medicines management across the interface. The perspectives of patients were gained through semi-structured interviews with 101 patients attending hospital outpatient clinics and eight medical inpatients. Patients were followed up after the hospital episode to detennine whether they had experienced any difficulties with their medicines. Three key outcomes emerged from the research. First, an improved understanding of the types of medicines management issues that arise when patient care is transferred across the interface. Second, four causes of sub-optimal medicines management across the interface were identified, a lack of awareness or misunderstanding of policy, inadequate inter- or intra-professional collaboration, impracticable or inflexible policy or flagrant violation of policy. Change management theory was utilised in order to confirm the presence of barriers that prevent medicines from being managed effectively at the interface and demonstrate why guidance has failed to improve the situation. Finally, this research has led to an improved understanding of the interface and its constituent dimensions which helps appreciation of the type of interventions that may be necessary in order to improve seamless care.