The potential interactivity of the antimicrobials miconazole and metronidazole in the induction of teratogenic effects was investigated in the present study. Drugs were injected at 60 mg/kg either individually or in combination to pregnant mice on gestation day (GD) 8, 9, or 10. Teratological assessments were carried out on GD 18. A potent teratogenic interaction resulted from miconazole-metronidazole co-administration, causing an increment in axial skeletal defects incidence. While, the individual exposure to miconazole or metronidazole produced axial skeletal defects at frequencies that did not exceed 5.6% in the various treatment groups, the percentage of fetuses with malformed skeleton reached 26% after co-exposure on GD 8 or GD 9. No significant synergism was noted when drugs were co-administered on GD 10. This study shows that a teratogenic interaction can result from miconazole-metronidazole concomitant exposure.