Adenovirus recombinants were constructed in which a copy of the major late promoter was inserted either upstream or in place of the promoter for early region 1A (E1A). The ectopic late promoter directs a 20- to 100-fold increase in the level of cytoplasmic RNA from E1A. The RNA is correctly processed at the normal splice and polyadenylation sites, and directs the in vitro synthesis of the full complement of E1A proteins. Furthermore, the novel transcripts are translated in vivo, since the recombinants are fully viable on HeLa cells notwithstanding the loss in one case of the intact E1A promoter.