Crude cottonseed oil (CCSO) containing 0.01% gossypol was evaluated in the present studies to record its effect on fertility of male and estrous cycle of female lesser bandicoot rat, Bandicota bengalensis Gray and Hardwicke. Laboratory feeding of bait (cracked wheat and powdered sugar in 98:2) containing 5 and 10% CCSO to female B. bengalensis for 13 days in no-choice feeding test, had no significant effect on the duration of the estrous cycle. However, laboratory feeding of bait containing 10% CCSO to male B. bengalensis for 15 and 30 days duration in a no-choice feeding test, significantly (P50.05) reduced sperm motility (%) and viability (%) in cauda epididymal fluid of treated rats compared to untreated ones. The weight of seminal vesicles of rats treated for 30 days was found to be significantly less (P 50.05) than that for rats treated for 15 days. No significant effect of treatment was observed on the breeding success of rats, diameter of seminiferous tubules, cell count and association of various germ cells in testis. Further studies may be conducted by increasing the duration of treatment or by using CCSO containing a higher concentration of gossypol.