Brain drain is one of the important aspects of development economics/Demographic transitions. A populous country has the potential to export human capital. There are so many determinants of Human Capital Outflow (HCO). Some like economic, social, and political drivers are already discussed in the previous studies. This study compares the impact of various classes of variables on the HCO. Furthermore, it gives recommendations for controlling HCO based on such results. Data is collected in the form of questionnaires from three rural and three urban areas of Peshawar. Random sampling is used. Probit models are used for comparing the significance of variables. The study shows that not only the classic variables, i.e. economic, social and political are important but also the newly introduced religious and environmental factors have a great impact on HCO. The forthcoming researchers can do further study by considering even more factors affecting the HCO. They can conduct studies for different areas and on different scales.