Abstract The colobus monkeys and gorillas of African forests share a strong tendency to depend on foliage during lean seasons. In many areas, both kinds of primate are threatened by habitat destruction. But while the total removal of natural habitat is clearly a major threat to the survival of many African forest primates, an analysis of survey data suggests that human predation tends to have a greater negative impact on primate populations than does selective logging or low-intensity bush-fallow agriculture. In the absence of hunting, the population density of colobus monkeys correlates with the protein: fibre ratio of mature tree foliage in their habitat, and the density of gorillas appears to be correlated with the abundance of terrestrial herbaceous vegetation. Because moderately disturbed forest can be relatively rich in high-quality lean-season folivore foods, such forest sometimes supports a higher density of folivorous primates than forest that has not been recently disturbed but that has been subject to hunting. Conservation plans for African forests should place more emphasis on the control of hunting and less on rural development, and long-range plans should also allow for the strong possibility of political instability.