We have mapped in the pig (Sus scrofa) the genes for zona pellucida glycoprotein 3 (ZP3), erythropoietin (EPO), and malate dehydrogenase 2 (MDH2) by somatic cell hybrid analysis in the pig genome. Previously, the gene for the T-cell receptor β cluster (TCRB) was assigned to SSC 18 and that for interleukin 6 (IL6) to SSC 9. However, statistical analysis of mapping data for ZP3, EPO, and MDH2 did not discriminate between SSC 9 and SSC 3. Porcine-specific PCR primers for ZP3 and IL6 were used to isolate probes from porcine YAC libraries. These two genes were mapped by FISH to porcine chromosome regions 3pter→p15 (ZP3) and 9q14→q15 (IL6). Comparative mapping considerations permit the tentative assignment of porcine EPO and MDH2 to 3pter→p15.