The teratogenicity of combined exposure to noise and cadmium was studied in mice. ICR mice were exposed to a wide octave-band of noise at 100 dB(C) for 6 h on d 7 of pregnancy in one of two ways: continuous exposure or intermittent (15 min on/15 min off). Cadmium sulfate at 1 or 2 mg/kg was intraperitoneally injected on d 7 of pregnancy. Four groups were exposed to both cadmium and noise. On d 18 of pregnancy, fetuses were examined for external and skeletal malformations. Another experiment was performed with two other patterns of noise exposure: continuous exposure for 3 h, and intermittent exposure (5 min on/5 min off) for 6 h on d 7 of pregnancy. In the groups exposed to continuous noise for 6 h, total percentages of malformed fetuses were significantly higher than that in the control group, but there were no significant increases of total percentages of fetal malformations in the combined treatment groups in comparison with the groups given the same dose of cadmium alone. The percentages of skeletally malformed fetuses in groups exposed to 6 h of continuous noise were significantly higher than in groups that received saline or the same dose of cadmium. There were no significant differences in the total percentages of malformed fetuses between the control group and the groups exposed to a total of 3 h of noise, whether continuously or intermittently. Although combined treatment with cadmium and noise resulted in an increase of total percentages of malformed fetuses compared to the same dose of cadmium alone, the interactions between cadmium and noise showed no synergistic effect on teratogenicity. The magnitude of teratogenicity due to noise is much weaker than that of cadmium, and is therefore easily masked by that of cadmium in statistical tests of the significance of differences.