The goal of this project was to identify conditions that result in development from the zygote or the 2-cell stage Sinclair miniature pig embryos to the blastocyst stage. Four media were selected, 2 that have been shown to result in in vitro development in domestic pigs (Hepes buffered Tyrode's medium and Whitten's medium), 1 that is compatible with similar development in the cow (CR-1), and 1 that is compatible with development in the mouse (CZB). One- and two-cell stage embryos from Sinclair miniature pigs were flushed from oviducts in Hepes buffered Tyrode's medium, allocated to 1 of the 4 media and cultured for 120 h. At the end of the culture period, embryos were morphologically scored and nuclei were counted. Morphology scores were lowest for Hepes buffered Tyrode's medium but were not different for Whitten's medium, CZB or CR-1. The highest (P < 0.07) number of nuclei was present in the oocytes cultured in Whitten's medium (21.3), with CR-1 (15.7) and CZB (16.5) not differing significantly. Similar to the morphology scores, Hepes buffered Tyrode's medium resulted in the lowest number nuclei (5.5). In a parallel experiment, domestic pig embryos were cultured in Hepes buffered Tyrode's medium versus Whitten's medium. The domestic pig embryos, while also developing better in Whitten's Medium, developed better in the Hepes buffered Tyrode's medium than did the embryos from Sinclair pigs. Thus, the Sinclair pig embryo develops best if placed in Whitten's Medium.