The periods of elevated temperature and high humidity has been longer since last ten years and cause problems in program of artificial insemination or at the efficiency of in vitro production of transferable embryos. The aims of this study were to evaluate the relationship between time of heat shock (0, 1, 2 and 4), during in vitro maturation and developmental competence of subsequent embryo after in vitro fertilization. The develpmentat rate and percetage of apoptotic cells were evaluated on matured oocyte and day 8. 41℃ Heat treatment after IVM culture significantly decreased the developmental capacity of IVF embryos. Also the number of apoptotic cell in COCs, morula and blatostcysts was started to increase at 2 hr heat treatment but did not affect on the rate of maturation. These results indicate that heat treatment for 2 to 4 hr at 41℃ have negative effects on maturation rate of COCs and lower the developmental competence of heat shocked oocyte derived embryos.