Abstract: 50 time-mated pregnant rats were divided into five groups and injected daily from gestational days 7 to 18 with either 2,2′,4,4′tetrachlorobiphenyl (PCB 47) at the dosage of 1.00 or 20.00 mg/kg body weight; or 3,3′,4,4′ tetrachlorobiphenyl (PCB 77) at the dosage of 0.25 or 1.00 mg/kg body weight; or sesame oil (control) to investigate the effects of fetal and lactational PCB exposure on reproductive behavior in male and female laboratory rats. Offspring were then tested for male sexual behavior: mount frequency, MF; mount latency, ML; intromission frequency, IF; intromission latency, IL; ejaculation latency, EL; post ejaculatory interval, PEI; hit rate and female sexual behavior; approach latency, AL; mount return latency, MRL; intromission return latency, IRL; post ejaculatory refractory period, PER; lordosis quotient, LQ. Measures were made at the age of postnatal days 70 to 91, and 97 to 101, respectively. The results showed that exposure to both PCB 77 and PCB 47 significantly reduced the LQ (84.4% for control, 76.0%, 67.8% for PCB 47 groups and 64.4%, 53.3% for PCB 77 groups; P<0.05) in the female offspring. There were no significant effects on AL, MR, IRL, PER (P>0.05) of the female offspring, or on MF, ML, IF, IL, EL, PEI and hit rate (P>0.05) of the male offspring.