The S1 endonuclease mapping technique was employed to characterize polyadenylated RNA molecules encoded by the African green monkey lymphotropic papovavirus (LPV) in B-lymphoblastoid cells of human origin infected with the virus. Two groups of stable transcripts of opposite polarities were identified and mapped. By analogy with other papovaviruses, these molecules were designated as "early" and "late" RNAs. The early transcripts include two RNA molecules consisting of a colinear 3' "main body" of about 1.9 kb spliced to 5' "leaders" of 0.26 and 0.60 kb, respectively. These molecules are presumably mRNAs encoding the LPV large T and small t antigens. Shorter, less abundant early RNA molecules have also been detected but have not been mapped. The late RNAs include three molecules, of which two consist of a common leader of 0.22 kb spliced to main bodies of 1.2 and 1.85 kb, respectively. The third late transcript of 2.3 kb is colinear. These late transcripts are presumably mRNAs encoding the LPV capsid proteins. A survey of the LPV DNA sequence published by M. Pawlita, A. Clad, and H. zur Hausen (1985, Virology 143, 196-211) allowed tentative assignment of the termini and splice sites of the various RNAs to nucleotides in the DNA sequence. The LPV transcription map is similar but not entirely analogous to those of polyoma virus and simian virus 40. These distinctions support a previous classification of LPV as a member of a new subgroup of the polyomaviruses.