A/J strain mice have a high spontaneous incidence of cleft lip (ICL) and/or palate. The primary palate-related effects of sevoflurane on developing A/J strain mouse embryos (embryos) were studied using a whole-embryo culture (WEC) system. This system could separate the direct effects of sevoflurane from those that are maternally mediated. A total of 205 10.5-d embryos were cultured for 24 h in either a control group (control gas: 95% O2 and 5% CO2) or sevoflurane-administered groups (1/4, 1/2, and 1 minimum alveolar concentration (MAC) with control gas) for 8 h. After 16 h, 11.5-d culture embryos were examined in terms of crown-rump length, number of somites, and protein content. Crown-rump length in the 1 MAC was significantly shorter than in the control group (p < 0.05). Protein content in the 1/2 MAC (p < 0.05) and 1 MAC (p < 0.001) was significantly lower than in the control group. The ICL showed no significant differences between each group. (The ICL rose with an increase in the sevoflurane concentration, but this was not significant). The positive findings in this study indicate that a WEC system is useful for studying the mechanisms of ICL (teratogenicity) associated with sevoflurane.