Biopesticides based on Heliothis nuclear polyhedrosis virus (NPV), one of the Baculovims group, are notable for their potency, specificity and safety. The virus constitutes a natural mortality factor in Heliothis populations on cotton (Wilson and Greenup, 1977) and other crops. It has evolved to produce vast amounts of infectious virus per infected insect. This can be exploited by laboratory mass production of the virus, and dissemination by the grower using conventional spray equipment. This paper is designed to give background to reports on &quote;Gemstar&quote; trials during the past two seasons. A brief history of its development as an insecticide in Australia is given in Table I.