The influence of culture temperature and gas atmosphere on in-vitro fertilization and embryo development was examined in the domestic cat. In Exp. 1, eggs were fertilized and cultured in 5% CO2 in air at 37, 38 or 39 degrees C. Experiment 2 evaluated the effects of 5% CO2 in air; 5% CO2, 5% O2 and 90% N2; and 10% CO2 in air. Fertilization (cleavage) and development to the morula/blastocyst stage were not influenced (P greater than 0.05) by variations in temperature and gas composition. Despite changing these culture conditions, egg cleavage averaged approximately 75% and greater than 80% of the 2-cell embryos proceeded to morulae in vitro. However, the partial in-vitro morula-to-blastocyst developmental block normally observed in this species was not removed.