The activities of viral and insect promoters were examined in a range of insect cell lines permissive and nonpermissive for the replication of the baculovirus Autographa californica nuclear polyhedrosis virus. Recombinant baculoviruses were constructed to place the bacterial chloramphenicol acetyltransferase gene under the control of promoters strongly active in the early, late, or very late stages of virus replication. In fully permissive cells, expression from a very late promoter was 2- to 3-fold higher than expression from a late promoter and 10- to 20-fold higher than expression from an early promoter or from a virus-borne insect promoter. In cell lines that do not support the efficient production of viral progeny, late-promoter-driven expression was similar to or surpassed very late promoter-driven expression. In nonpermissive insect cell lines, expression driven by an insect promoter derived from Drosophila melanogaster was higher than expression from the three viral promoters and was especially high in the Drosophila cell line tested. Surprisingly, late-promoter-driven expression, which is dependent on DNA replication, was higher than early-promoter-driven expression in three of four nonpermissive lines. In contrast, very late promoter-driven expression was quite limited in nonpermissive cell lines. The results indicate that the promoter used to drive foreign-gene expression strongly influences the range of insect cells which can efficiently support the production of the foreign protein during infection with recombinant baculoviruses.