The report describes the assessment of the potential environmental impacts of genetically improved viral pesticides, including an evaluation of the properties of the foreign gene product(s) and the biological properties of the altered virus itself. The current field release studies are collecting much of the information which will be needed to assess the environmental safety of these new pesticides. Of primary concern will be the cost-to-benefit ratios as determined by production costs, stability, application, technology, and field efficacy. Despite the improvements afforded through biotechnology, it is clear that viral and other microbial pesticides will only reduce, not eliminate, the agricultural requirements for synthetic pesticides. Even so, biological pesticides are among the best solutions to reducing crop losses in the absence of ecological disturbances and potential health hazards.