6-Dimethylaminopurine(or 6-DMAP), a specific inhibitor of protein phosphorylation, was found to inhibit meiosis reinitiation in mouse, cow and pig oocytes by preventing chromatin condensation and GVBD. The purpose of this study was to examine the effect of 6-DMAP on mouse oocytes in metaphase II. This study found that 6-DMAP could activate mouse oocytes(M II), and the activated oocytes could develop to the morula or blastocyst stage.Oocytes were collected from superovulated Kunming albino female mice 18-19h after hCG injection. Oocytes were placed in CZB medium with 2mM/L 6-DMAP or activated with 7% ethanol. After treatment, the oocytes were washed three times with M 2 medium and cultured in CZB medium at 37°C in the humidified atmosphere of 5% CO 2 and air. Oocytes with 1-2 pronuclei were considered activated 6h after activation treatment. The results were as follows:To compare with the ethanol control group, activation and cleavage rates were significantly lower in the 6-DMAP treatment groups, but 70% or more of activation and cleavage rates could be obtained in the 6-DMAP treatment groups by selecting an appropriate exposure time. It varied in activation rate and cleavage rate among 6-DMAP treatments. The activation rate of oocytes cultured in 6-DMAP for 1h was higher than that cultured in 6-DMAP for 0.5h, and there were no enhancement in activation rates by increasing exposure time from 1h to 3h. The averavage rate of activated oocytes declined gradually as the exposure time increased from 0.5h to 3h. Some oocytes activated by 6-DMAP could develop to the morula or blastocyst stage. The activation effect of 6-DMAP may be explained by the following: 6-DMAP induces MPF(Maturation Promoting Factor) or its relevant protein dephosphorylation or inhibits their phosphorylation. Thus, MPF activity declines in response to 6-DMAP or dephosphorylation and pronuclei are formed in oocytes.