More than 30 years after the first outbreak of Marburg virus disease in Germany and Yugoslavia and 20 years after Ebola hemorrhagic fever first occurred in central Africa, the natural history of filoviruses remains unknown. In 1979 and 1980, animals in the Democratic Republic of the Congo and Cameroon were collected during the dry season near the site of the 1976 Ebola hemorrhagic fever epidemic. The study objectives were to identify local animals and search for evidence of Ebola virus in their tissues. A total of 1664 animals representing 117 species was collected, including >400 bats and 500 rodents. Vero and CV-1 cells and IFA and RIA were used for virus and antibody detection, respectively. No evidence of Ebola virus infection was found. This study was limited in time and animal collections and excluded insects and plants. Long-term, prospective, multidisciplinary comparative studies will yield more information than will repeat short forays on the ecology of filoviruses.