Neonatal female rats received intracerebral implants of testosterone propionate (TP) in paraffin, paraffin alone, cholesterol alone, subcutaneous TP, or no treatment. Only animals with intracerebral TP developed the anovulatory syndrome with persistent vaginal estrus. The most consistent effects and the earliest ages at onset of the syndrome were seen with implants in the ventromedial-arcuate hypothalamus.