In December 1997 and January 1998 we travelled to the northern section of the Salonga National Park in the Democratic Republic of Congo. The park is the largest African rain forest reserve, and was created in 1970 to protect endemic species such as the bonobo Pan paniscus and the Congo peacock Afropavo congensis. However, hardly any data exist on the status of animals in the park. In order to collect basic information, we set up camp at four sites along two rivers, where we followed long trails deep into the forest. A total of 7.5 km line transects were cut from three sites, along which all evidence of large mammals was recorded. Our data indicate that key forest species, including bonobo, bongo Tragelaphus euryceros, black mangabey Lophocebus alterimus and leopard Panthera pardus, are present in reasonable numbers in the part of the park we explored. Bonobo density was calculated at 1.15 animals per sq km, based on nest counts. Some elephants Loxodonta africana survive, despite the enormous hunting pressure. Conservation measures to protect the animals need to be taken urgently.