The effect of inhaled sulfuric acid (H2SO4) on embryonal and fetal development was assessed in CF-1 mice and in New Zealand white rabbits. Both species were exposed for 7 hr/day to 0, 5, or 20 mg H2SO4/m3 during the period of major organogenesis (mice, days 6 through 15 of gestation; rabbits, days 6 through 18 of gestation). Little evidence of toxicity was seen in the fetuses of mice or rabbits exposed to H2SO4. Slight maternal toxicity was seen at 20 mg H2SO4/m3 in both species. Teratogenicity was not observed in either mice or rabbits exposed to H2SO4.