It can be suggested that the ‘economic development’ of most Third-World nations today will be reflected in two distinct but interrelated processes: (1) a rise in economic productivity and in real incomes, and (2) a reduction in fertility and a corresponding slowing down in the rate of population growth.1 Historically, an increase in both the number of cities in a country and the number and proportion of the population living there, has been closely associated with both these processes. Accordingly, as urbanisation proceeds in Africa it might logically be assumed that economic growth and demographic modernisation are also taking place. It is our purpose in this brief article to offer a partial explanation for the fact that this historical association has not characterised recent trends in the continent.