Universitas terbuka (UT) as a higher open and distance education institution has been carrying out students' assessment in the form of paper and pencil and online examinations. This study was conducted to determine the effectiveness of the implementation of the Online Examination System (Sistem Ujian Online=SUO), in terms of the reliability (robustness) of SUO applications, the readiness of Human Resources in implementing an online exam, the infrastructure that supporting SUO, and the student responses. The results showed that SUO application and support application had been well developed by UT, proven that SUO have been in operation in 30 out of 37 UT regional centers in 2010. Students did not face many problems in registering in the online exam. Infrastructure and human resources were considered satisfctory. Respondents also said that SUO was very flexible in terms of choosing the exam schedule and getting the immadiate feedback. Based on the research results, a SUO model is described in several bussness processes, which include the preparation, execution, processing exam result, as well as supervision and evaluation. In the future UT still needs to improves facilities, infrastructure and quality of human resources that can support the online exam. The implementation of online exam relies heavily on information technology (IT) and it is expected that SUO is adaptable with this rapidly changed technology.