The social context of sexual relations is important in understanding the AIDS epidemic. So far, HIV in Pakistan has spread by heterosexual contact and blood transfusions. The magnitude of the problem is difficult to assess but health authorities estimate between 10,000 to 12,000 HIV infected people. This paper outlines that rapid urbanisation, together with single migrant workers, deported HIV infected expatriates, exploitation of women and easy availability of narcotic drugs, especially in the metropolis of Karachi, are some important factors that may be responsible for the spread of HIV in Pakistan.