Preliminary results from the Tanzanian census of 1988 are examined against the background of two decades of policies attempting to influence the distribution of population within the country. The overall rate of population increase has slowed down, as has the rate of urban population growth. However, the latter is very powerfully influenced by a significant reduction in the rate of growth in Dar es Salaam. Elsewhere, urban areas continue to grow very rapidly. Along with this pattern of population concentration, a degree of population dispersal is also evident, as a number of formerly lightly populated areas have recorded large percentage increases in population. A major cause for concern is that many of these areas have demonstrated various aspects of environmental degradation for some time. It is concluded that spatial planning policies have had only a limited impact upon the regional distribution of population in Tanzania in the 1978–88 period, and that ‘spontaneous’ processes have been far more significant.