Four hundred eight-cell mouse embryos were cultured in vitro in either polystyrene (plastic) dishes (Exp. 1) or watch glasses (Exp. 2) to analyze the toxicity potential of absorbed-retained ethylene oxide (EtO). Culture dishes were gas-sterilized with Anprolene equipment and allowed to aerate (21 C) for varying durations. Post-sterilization EtO residues, as determined by weight measurement, were eluted from polystyrene dishes at an exponential rate. After 1 wk of aeration, .625 mg EtO was retained/g of polystyrene product. To determine the effect of EtO residue on in vitro culture, embryos were collected from superovulated donor mice (C57BL/6N), pooled in a modified Dulbecco's phosphate buffered saline (PBI) medium and then randomly allotted to dishes subjected to various aeration durations. Embryos were cultured in Whitten's medium +3 mg/ml bovine serum albumin (BSA) under a humidified 5% CO2 in air atmosphere at 37 C. Gross assessments of embryo development were made using standard morphology and quality grading systems and a fluorescein diacetate staining assay. In Exp. 1, embryo development was retarded at the 8- to 16-cell stage when less than or equal to 12 h aeration of polystyrene dishes was permitted. Aeration for 24 and 36 h resulted in suboptimal embryo development with fewer (P less than .01) blastocysts and greater degeneration rates at 48 h of in vitro culture compared with the control (manufacturer-packaged dishes, no EtO) and 1-wk aeration treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)