With the advancement in information technology, online assessments are getting more attention and online examinations are regarded as important parts of online learning. Online examinations can be easily taken by remote students, help the students get exam results quickly and save their time; online examinations also aid instructors in collecting students' exam answers and generating the exam reports effectively. In addition, online examinations can help reduce cost and save trees for our world. Multimedia elements like images, graphics, video and audio have been widely integrated into online learning environments. They not only help instructors design more engaging online learning content, but also help provide more interactive and pleasant learning experience for learners. However, integrating multimedia elements into online examination systems is rarely reported. Multimedia elements generally consume amounts of computing resources in a separated software system running on a single computer. "Software-as-a-Service (SaaS)" has become a new software paradigm and cloud-based software systems are becoming more attractive due to their dynamic scalability and effective usage of computing resources. Yet, how to effectively integrate multimedia elements into a cloud-based software system for online examinations is not significantly investigated. Although a variety of online-assessment tools have been developed, few of them adopt the "Software-as-a-Service (SaaS)" paradigm and most of them focus on the assessment in a specific domain or an application area with short of multimedia elements. There is a lack of a comprehensive software solution for online multimedia examinations. This thesis tries to utilize the "Software-as-a-Service (SaaS)" paradigm, design and develop a cloud-bAsed softwaRe systEm for oNline multimediA examinationS (ARENAS), and explore a comprehensive software solution for the online assessment field. ARENAS employs a multi-tiered client-server architecture and includes five subsystem modules: user module, question repository module, exam module, exam report module and configuration module. The developed cloud-based software system can present online questions with multimedia elements, and also support a myriad of question types, flexible accounts to the exam-takers, randomized question order in an online exam, flexible grading mechanisms, and analytical exam reports. For instructors, the developed system can help design more engaging online questions; for exam-takers, the developed system can help provide more user-friendly experience; for other educators and researchers, the design and development processes of ARENAS can be taken as a reference to designing and developing other large-scale cloud-based educational software systems. / Master of Science