Mouse two-cell embryos of block (ICR) or nonblock (F1 of C57BL x DBA) strains were cultured in modified Chatot, Ziomek, and Bavister medium, supplemented with bovine serum albumin or polyvinyl alcohol, a synthetic macromolecule. The supplementation did not influence morula compaction and blastocyst formation, mean cell numbers of total blastomeres, inner cell mass (ICM) cells and trophectodermal (TE) cells in blastocysts, rates of pregnancy and delivery, mean litter size, number of implantation spots in pregnant females, and the expression of several genes related to pluripotency, organogenesis, and implantation.