Four amino acid analogues, imidazole, canavanine, p-fluorophenylalanine, and ethionine, were tested in diets for their effects on inhibiting reproduction in the female dipterous parasitoid Pseudosarcophaga affinis auct, nee Fallén. Effects of diets lacking in corresponding amino acids also were studied. Diets deficient in methionine and supplemented with ethionine affected reproduction during the 1st and 2nd oöcyte-growth cycles, whereas diets deficient in histidine, arginine, or phenylalanine, or those supplemented with their respective analogues, affected only the 2nd oöcyte-growth cycle. The various effects observed were inhibition of oöcyte growth, delay or lack of yolk deposition, and irregular ovulation and parturition. Lack of effect in the 1st oöcyte-growth cycle is presumably due to the carryover from the larval stage of nutrients required for oöcyte-growth. It is suggested that amino acid analogues offer promise not only for reducing insect fecundity but also as tools in research on insect reproductive metabolism.