We propose an ecological study of the macaques of Sulawesi, focusing on population status, distribution, habitat selection, niche specialization, and interspecific relationships. The island of Sulawesi (Celebes) has four to seven species of macaques, more than any comparable geographic area. This offers unique opportunities in Asian primatology for the study of interspecific relationships, competition, and niche separation in the genus Macaca. One of the species on which we will concentrate, Macaca nigra, also known as the Celebes black ape or black macaque, is of special biomedical significance since it is known in captivity to have a high prevalence of diabetes. Very little is known of its natural history and population biology in nature. This two-year study will obtain field data on the geographic and ecological distribution of all species of Sulawesi macaques, their population status, group sizes, sex and age ratios, birth rates, and population trends. Behavioral data will be obtained on reproductive behaviors, parental care, food habits, foraging patterns, movements, polyspecific groupings, and commensal relationships with the human population. We will emphasize the study of two pairs of species: Macaca maura and M. tonkeana, because of their known polyspecific and commensal relationships; and Macaca nigra and M. nigrescens, because they represent the most extreme evolutionary divergence from the ancestral stock of macaques, the least understood members of the genus, and the most significant in terms of health-related research. We will collaborate with a field program of serological surveys for retrovirus antibodies being undertaken by Drs. Nicholas Lerche, Preston Marx, and Linda Lowenstine of the California Primate Research Center, and with blood glucose screening for diabetes in Macaca nigra under the guidance of Dr. Charles Howard of the Oregon Primate Research Center.