Of all the climatic variables in the environment of termites in southern Kenya, only rainfall shows marked seasonality and unpredictability. But despite the great variability in rainfall patterns, the populations of termite mounds of various species in three well-separated study areas remained remarkably constant over a period of 6½ years. This provides good evidence for the effectiveness of the termites' control of their nest environments, and suggests that their populations are close to their carrying capacities. New colonies appeared either as new mounds or as recolonisations of old ones, the latter being less frequently recorded but having higher survival rates. The appearance of new colonies of Macrotermes michaelseni followed years of higher rainfall; the opposite was true for M. subhyalinus. Numbers of old colonies dying were roughly equalled by new colonies surviving. For the largest mound population, that of M. subhyalinus at Selengei, colonies in larger mounds had higher survival rates, as did those which had no close neighbours. Few colony deaths were attributed to ants, but more to aardvarks Orycteropus afer, particularly in wetter years, and more in the apparently softer mounds of M. michaelseni. Mounds containing live populations usually increased in size but all mounds lost soil by erosion. However, the whole process was so slow that turnover of soil was less than 1.0 m³.ha⁻¹.yr⁻¹.