A considerable amount of work has been done during the last 20 yr to genetically enhance the efficacy of baculovirus insecticides. Following construction of a genetically altered baculovirus, laboratory bioassays are used to quantify various parameters of insecticidal activity such as the median lethal concentration (or dose) required to kill 50% of infected larvae (LC₅₀ or LD₅₀), median survival time of larvae infected at a fixed dose (ST₅₀), and feeding damage incurred by infected larvae. In this chapter, protocols are described for a variety of bioassays and corresponding data analyses for assessment of the insecticidal activity or host range of baculovirus insecticides. Methods are also provided for baculovirus inoculation of larvae using a microapplicator for determining ST₅₀ or for examining physiological effects.