In this study, a simple time-lapse video recording system was used tocompare developmental kinetics of female and male bovine embryos producedin vitro. Following embryo sex determination, the timing of each cleavageup to the 4-cell stage was compared between the sexes from the videotapesafter culture in the presence and absence of glucose. In the secondexperiment, the consequences of exposure to a time-lapse video recording(TL) environment were studied by culturing embryos further until day 7in an incubator, followed by collection and sex determination of morulaeand blastocysts. In the absence of glucose, female embryos cleaved earlierthan male ones. In the presence of glucose, however, male embryos cleavedearlier than female ones. There was no difference in the number ofmorulae/blastocysts in the absence of glucose, but in the presence ofglucose more male than female embryos reached the morula and blastocyststage. Exposure to the TL environment itself also had a sex-relatedeffect, being more detrimental to male than female embryos. The differencein the number of functional X chromosomes between the sexes during earlypreimplantation development could explain these findings. In females, anincreased capacity for oxygen radical detoxification through the pentosephosphate pathway could result in a reduced cleavage rate. Furthermore,glucose may influence the expression of enzymes located on the Xchromosome. According to these results, a simple time-lapse videorecording system is suitable for investigating embryo developmentalkinetics and perhaps for the selection of embryos with the greatestdevelopmental potential.