The following sodium chloride controls and functional analogs of sodium salicylate were compared for teratogenic properties by ip administration to Sprague-Dawley rats on gestational (copulation evidence = day 1) days 9-11 or 12-14: sodium chloride, 600,90 mg/kg; sodium salicylate, 500, 283, 158, 50 mg/kg; sodium benzoate, 1000, 315, 100 mg/kg; and phenol, 200, 63, 20 mg/kg. On days 12-14, fetal body weight was reduced from high control dose by high doses of all three drugs: 5.25 i 0.17; 4.22 f 0.06; 4.56 & 0.05; 4.64 + 0.08 g (respective to listing above). Gross anomalies were not observed. In utero deaths were increased by both sodium salicylate and sodium benzoate: 1, 26, 12, 1 y0 (respective to listing above). On days 9-11 fetal body weight was reduced from control by sodium salicylate, B 158 mg/kg, and sodium benzoate, 1000 mg/kg, but not by phenol: 5.10 i 0.03, 3.98 & 0.05, 4.75 i 0.04, 4.12 rt 0.07, 5.09 i 0.04 g, respectively. In utero deaths were increased by high doses of all of the sodium salts, but not by phenol; 15,5,99, 16,12,4x. Gross anomalies were observed with sodium salicylate, 500, 283, and sodium benzoate 1000 mg/kg. In conclusion, at equitoxic doses the teratogenicity appears to be associated with carboxyl moiety. The hydroxy group may contribute to, but is not necessary for, teratogenicity. (Supported by NIH Grant Nos. GM-12,675 and GM0141.)