Chronic ingestion of ethanol produces a variety of effects on female reproductive function, depending on the dose and the exposure time but the mechanism of alcohol-induced ovarian failure has been little studied. Also the effects of chronic ethanol consumption on the oocyte quality in relation to morphological alterations and PGE synthesis by the oocyte cumulus complexes (OCCs) have not been described. In this study, immature female mice were treated with 10% ethanol in drinking water for 30 days. Then they were induced to superovulate, and at 14, 16 and 20 h post-hCG the quality of the ovarian and oviductal oocytes and PGE production by OCC was determined. At 14 h post-hCG, the percentage of oviductal immature oocytes was increased in the ethanol-treated females (P< 0.05). At 16 h post-hCG, the percent of oviductal activated oocytes was higher in the treated females (P< 0.05), and the ovarian immature oocytes were decreased as compared to the control females (P< 0.05). At 20 h post-hCG, the ethanol-treated females had higher percents of activated oocytes in the oviducts and in the ovaries (P< 0.05) with respect to the controls. PGE synthesis by OCCs, assessed by RIA, was decreased in the treated female mice (P< 0.001). In summary, moderate chronic ethanol treatment in immature female mice can produce morphologic abnormalities in the oocytes (high parthenogenetic activated rates) and altered PGE production in the OCCs.