A preliminary map of the frog virus 3 (FV 3) genome was constructed by hybridization-selection of mRNAs to cloned DNA fragments and translation in reticulocyte lysates. FV 3 mRNAs were hybridized to KpnI, HindIII, and SalI restriction fragments representing the entire FV 3 genome. Two different hybridization conditions were employed in order to discriminate between the hybridization of early and late mRNAs. A total of 43 major and 18 minor early genes and nine major and three minor late genes were mapped. A 24 kb region comprised of the KpnI D, H, and E fragments encodes 8 of the 12 late genes that were mapped.