Rats maintained on a diet deficient in retinol and retinoic acid were given a diet containing retinoic acid for 21-29 days after the start of weight loss. The testes of four of these rats were studied. Spermatogonia of all types were observed, though in lower numbers than in controls, and their mitotic activity was normal. Normal preleptotene spermatocytes were encountered, but no normal spermatocytes in further stages of development were seen. Pale cells that appeared to be in prophase were observed. It was concluded that, in retinol-deficient rats maintained on retinoic acid, the spermatogonial population is qualitatively normal, but quantitatively subnormal, while spermatocyte development is qualitatively and quantitatively abnormal. No evidence of spermatogonial arrest or any other form of synchronization was found in testes of these rats, but when the remaining rats were injected with retinol, the seminiferous epithelium did show stage synchronization at 36 and 128 days after the injection.