In a wild-type strain of Drosophila melanogaster Meigen, the antijuvenoid precocene I reduced primary sexual receptivity in a dose-dependent manner; exposure to 0.80 μmol halved mating by virgin females in a 1-h test. Precocene-treated females rejected courting males for longer times than control females, but the rates of rejection signaling per unit time were unaffected. Precocene I slowed ovarian growth and markedly reduced oviposition; exposure to 0.14 μmol of precocene decreased oviposition by about half. Protein deprivation severely reduced ovarian volume and lowered primary receptivity in 3-d-old flies. Protein-starved females decamped from courting males more than yeast-fed females did at all the ages tested, whereas both age and diet affected the rates of stereotyped rejection signals. Precocene II did not affect sexual receptivity, whereas exposure to 70–140 μmol of ethoxyprecocene reduced sexual receptivity significantly.