Female crayfish, Procambarus clarkii, were exposed to 10 ppm naphthalene to determine its effect on ovarian development. Ovaries were removed for examination after 1, 2, 4, 6, 8, 10, 12, and 15 days of exposure to the naphthalene. Crayfish that had been exposed to naphthalene for 15 days were then returned to clean freshwater for 1, 2, 4, 5, 7, 10, and 15 days to determine whether the ovaries would recover from the naphthalene exposure. The ovarian index, which reflects the weight of the ovary, decreased gradually over the 15-day naphthalene exposure period. The previtellogenic and vitellogenic oocytes degenerated. Intense atresia along with yolk resorption led to this decrease in the ovarian index. In contrast, the ovaries of the control crayfish developed into ripe gonads. However, immature oocytes reappeared in the ovaries of the crayfish subjected to depuration, which suggests that the ovary of P. clarkii can recover from naphthalene-induced atresia.