An adenovirus-SV40 recombinant has been constructed in which the SV40 early region, joined to a copy of the adenovirus major late promoter, was substituted for a small portion of the adenovirus late region and all of early region 3. The inserted sequence functions as a separate transcriptional unit, using the ectopic adenovirus promoter, SV40 splice sites and SV40 polyadenylation site. The RNAs produced lack both the second and third members of the tripartite leader normally found on adenovirus late RNA, yet are translationally active, directing the synthesis of substantial amounts of SV40 T antigen. The recombinant may serve as a model vehicle for the abundant expression of other eucaryotic genes inserted into the adenovirus genome.