There is much historical evidence of the spread of disease through human mobility. Today in spite of medical advances and international heahh measures there is still much cause for concern. There Is now more mobility, facilitated by modem transport and sometimes precipitated by major natural and man-made disasters. Redistribution of population is occuring in the developing world, particularly massive rural-urban movements. Population mobility has contributed to the transmission of malaria and prejudiced programmes for control and eradication; but mobility and other human factors have not bean adequately studied. Parasites and vectors receive more attention than do people. Epidemiological studies need to pay greater attention to the nature and variety of population movements and to their differing Impacts upon disease and health. It Is essential to distinguish between migration (involving change of residence) and circulation (movement away from residence with subsequent return). In tropical Africa various spatial and temporal dimensions can be applied to differentiate within these two major categories of mobility. In turn there are various associated physical and psychological health hazards.