The economic depression of the late 1980s has made workforce groups particularly in the medical industry to look beyond their nose and seek greener pasture somewhere outside their environment, at all costs. This economic situation deeply affected the medical groups that migration became the chorus of the medical personnel. This study examined the factors that influence brain drain among the medical personnel in Nigeria, using a selected University Teaching Hospital as a case study. A pretested 5-point Likert scale questionnaire was administered to 85 randomly and purposively selected medical personnel to determine causes of migration and the corresponding effect on medical services, and development of future medical personnel in the country. The survey made use of both historical and descriptive research methods. The data gathered through the questionnaire were subjected to simple descriptive statistical analysis. The results of the survey showed that migration decision was highly influenced by the conditions within the organization rather than the pull factors. The motivation of employees was at very low level, with inability to meet the physiological needs ranked first by SO.6 percent of the respondents. Brain drain was also found to have significant negative effect on medical services, training and development of future medical personnel. For the internal or push factors, better working condition was the major reason for migration as indicated by 87.0 percent of the respondents. The study, therefore, concluded that the desire for better life is the most important factor for migration decisions, and certainly brain drain is the fall-out of economic depression. Consequently, the study recommended policy design and implementation of economic enhancement status of medical personnel in order to reverse brain drain to brain gain.