Abstract This report presents a synopsis of recently published work in our laboratory on the molecular biology of the insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV). The following studies have been summarized. 1. (1) On the mode of transcription of the AcNPV genome in insect cells. 2. (2) Translation of proteins encoded in the 8.12 to 85.0 map unit segment of AcNPV. 3. (3) Inserts of insect cell DNA in the AcNPV genome. 4. (4) Expression of influenza (fowl plague) virus haemagglutinin in Spodoptera frugiperda insect cells, and successful immunization of chickens. 5. (5) Synthesis of the influenza virus haemagglutinin in insect larvae by recombinant AcNPV. This insect virus system will continue to serve as a model for research on the molecular biology of insects. Moreover, the baculovirus system has been recognized as a very efficient and safe eukaryotic expression vector.