This paper reports the results of the first detailed census of the eastern lowland gorillas ( Gorilla gorilla graueri) in Kahuzi-Biega National Park. Fourteen groups and five lone males totalling 223 gorillas were estimated by night nest counts. The presence of secondary forest appears to be an important factor influencing gorilla distribution within the park. Gorillas tended to concentrate in areas of extensive secondary forest where abundant food and cover was available. Large areas of the park (58%) did not contain suitable gorilla habitat and consequently supported no groups. The population density of gorillas in the park was calculated to be 0·37/km 2. The population is considered to be relatively stable or increasing. To ensure the continued protection of the gorillas and maintenance of suitable habitat, follow-up census studies, a long-term park management plan, along with the development of tourism, are recommended.