Soil-scratching behaviour by western lowland gorillas (Gorilla gorilla gorilla) was recognized in a field study in the Ndoki forest of northern Congo. The purpose of this behaviour was probably insect eating although the harvest of insects was likely to be relatively poor. The seasonal variation in the appearance of insects found in faecal samples coincided with the frequency of soil-scratching traces. Soil-scratching behaviour was considered not to make a large nutritional contribution for gorillas.