Teratogenicity of test substance 5601-56-1 (Naphthalene) was evaluated in 4 groups of 18 New Zealand White rabbits dosed 0, 40, 200, and 400 mg/kg/day by gavage gestation days (GD) 6-18. Maternal weight gain was not significantly reduced in any dose group. Food consumption decreased significantly in high dose group GD 7-15, but increased GD 23-25 and 27-29. No compound-related maternal mortalities were reported. At 40 mg/kg, 2 does aborted and 1 delivered prematurely (GD 29). Dose related effects on does were excessive facial grooming, decreased activity, dyspnea, infrequent loose stools or diarrhea, salivation, nasal and ocular discharge, body drop, and cyanosis. No significant differences were ob- served between treated and control groups in total number of implantations, corpora lutea, viable and non-viable fetuses, fetal sex distribution and post- implantational losses (early and late resorptions). Uterine weights were not reported. The 9 fetal deaths on Caesarean delivery GD 29 were judged coincid- ental since fetal physical characteristics were not dose-related. Fetal mal- formations were considered spontaneous. In the high dose group, a significant decrease in the number of 13th right-sided ribs was reported secondary to the total number of 13th paired ribs observed. Statistical differences were deter- mined by one-way analysis of variance.