Five isolates of three entomogenous fungi were bioassayed for their infectivity to second instar larvae of Spodoptera litura Fab. by spraying the host larvae with the conidial suspension in the laboratory. Of them, Beauveria bassiana (Bals.) Vuill. (Bapatla isolate) was found to be the most virulent recording the lowest LC50 of 19.90 í— 105 conidia ml-1. Tbe LC50 values of the Bangalore and New Delhi isolates of B. bassiana, Paecilomyces fumosoroseus (Wize) Brown and Smith and P. farinosus (Holm ex Gray) Brown and Smith ranged from 5.55 í— l08 to 5.58 í— 109 conidia ml-1, Bioassay of second, third and fourth instar larvae of S. litura for their susceptibility to Bapatla isolate or B. bassiana showed that susceptibility decreased with increase in age of the larvae in terms of both LC50 and LT50.