AbstractMouse embryo culture has been established and applied in the study of the causal mechanisms of abnormal development. Mouse embryo culture can be used as an experimental system to examine the influence of teratogen on early development, together with investigations using developmental engineering such as chimera, transgenic mice and nuclear transfer. We combined mouse embryo culture with embryo transfer and chromosome analysis, and studied the relationship between environmental factors (including maternal factors) and genetic predisposition in developmental abnormalities in the embryos of diabetic mice.In mouse embryo culture from one‐cell to the blastocyst stage, fertilized eggs were incubated in modified Whitten's medium and mixed gas (5% O2, 5% CO2and 90% N2) at 37°C for three days. β‐Mercaptoethanol 20 μM and EDTA‐2Na 100 μM were added in order to overcome “two‐cell block’ in which two‐cell stage embryos could not develop further. Under theses conditions, from 55 to 100% of the cultured one‐cell stage embryos developed into blastocysts depending on the strain.For chromosome preparation, Mikamo and Hamaguchi's method (1975) was modified. This method can be applied from one‐cell to pre‐implantation stage embryos, and allows a higher rate of success (63% of prepared embryos) in preparing chromosome slides than that reported in the literature. Using improved methods of embryo culture, embryo transfer and chromosome analysis, we have obtained evidence that both environmental and genetic factors are the causes of malformation during diabetic pregnancy in mice. Mouse embryo culture associated with chromosome analysis is a useful procedure, and offers important data for the clarification of the causal mechanisms in deve