The purpose of this study was to evaluate the effect of MEHP on in vitro maturation of mouse oocytes and resulting embryo development. Denuded oocytes (DO) were cultured in maturation medium supplemented with 0, 50, 100, 200 and 400 microM levels of MEHP for 24 h. The matured oocytes then were fertilized and cultured for 4 days. The percentage of Germinal Vesicle (GV) stage oocytes were significantly higher in 200 and 400 microM MEHP treatment comparing to the control (P < 0.05). The proportion of oocytes that progressed to the metaphase II (MII) stage was significantly decreased by adding of MEHP in a dose related pattern. The 2-cell embryo formation was significantly decreased with 400 microM treatments than the control. Moreover with further culture in experimental groups none of the embryos comparing to that of the control group were developed to morulla stage (P < 0.05). These results indicate that MEHP could negatively modulate mouse oocyte meiotic maturation in vitro and embryo development, suggesting possible risks for human and other mammalians reproductive health.