FD & C Yellow No. 5 (tartrazine) was given to Osborne-Mendel rats by gavage at dose levels of 0, 60, 100, 200, 400, 600 or 1000 mg/kg body weight/day on days 0-19 of gestation. No maternal or developmental toxicity was observed when the rats were killed on day 20. The mean daily food consumption for the entire period of gestation was significantly greater in the females given 1000 mg/kg body weight/day than in the controls, but maternal body-weight gain was not affected. No dose-related effects were observed in implantations, foetal viability or external foetal development. Foetal skeletal and visceral development was similar among foetuses from all groups. At the doses given, FD & C Yellow No. 5 was neither toxic nor teratogenic.