Ochre-bellied flycatchers (P. oleaginea) were studied in Trinidad over a 4-yr period, 1957-1961. Sixty occupied nests were found and 135 individuals were examined. The sexes were distinguished by wing-length and degree of emargination of the outer primaries. This species is the most abundant forest flycatcher in Trinidad and its abundance is tentatively attributed to the fact that it is to a large extent frugivorous. Males sing and display within a loosely defined lek area in which individuals are usually within earshot but not visual range of one another. Breeding success in the study area was very low (12% of nests started), failures being attributed to predation and also to interference from conspecifics. This species appears to illustrate an early stage in the evolution of lek behavior. Important predisposing factors for this habit include frugivory, nest type and probably also the female''s ability to regurgitate relatively large amounts of food for the young at each visit to the nest.