The pathology caused by baculoviruses in insect popula­ tions was described centuries ago, notably in the larvae of insects such as the silkworm (Bombyx mori) which has been appreciated for the quality and beauty of its products. In the 1940s baculoviruses and their structure and physiolo­ gy were intensively investigated, particularly by Bergold's group in Tiibingen. The following decades saw excellent progress, laying a solid virological base for later investiga­ tions on the system. Further studies mushroomed in the 1970s with the advent of tissue culture systems for insect cells which eventually facilitated the molecular biological approach that came to the fore in the 1980 s. One of the reasons for pursuing research on the baculo­ virus system was the prospect of eventually using these vi­ ruses as insect pest control agents. While this practical as­ pect may appeal to many, molecular biologists had addi­ tional reasons to be interested in baculoviruses. Here was a large DNA viral genome, probably fraught with problems of replication and regulation that hopefully would open inroads into the molecular biology of interesting insect cell systems. In the days when genetechnology promises laurels, and after several virus systems had been skilfully exploited as highly efficient eukaryotic expression vectors, it came as no surprise that baculoviruses were also investigated in that respect. Indeed, the Autographa californica nuclear po­ lyhedrosis virus became a good vector. Insect cells also seem to collaborate in modifying and processing the gene­ technologically synthesized polypeptides.