The reproductive and teratogenic effects of lidocaine were studied in 155 Sprague-Dawley rats chronically implanted with osmotic minipumps. Three different lidocaine doses were used as follows: a low dose (100 mg · kg−1· day−1); an intermediate dose (250 mg · kg−1· day−1); and a high dose (500 mg · kg−1· day−1). In the low and intermediate dose groups, lidocaine was administered for two weeks before mating and throughout pregnancy to evaluate reproductive and teratogenic effects. In the high-dose group, lidocaine was administered from days 3 to 17 of pregnancy to evaluate teratogenic effects. On day 21, cesarean section was performed and all of the 1,040 offspring, including those from control and positive control (retinoic acid) groups, were preserved and subsequently examined microscopically to detect external, visceral, and skeletal abnormalities. None was found in lidocaine-treated groups; reproductive indices also were normal. The only treatment effect was a reduction in mean fetal weight in the high-dose group. In a subsequent experiment this was found to be secondary to slightly delayed fetal development. It is concluded that lidocaine is devoid of significant adverse reproductive and teratogenic effects in Sprague- Dawley rats.