A field experiment was carried out during 2007-08 and 2008-09 on farmer’s field comprising of Bt cotton CV, Vikram-5 following randomized block design with four replications and six treatments to evaluate the bioefficacy of buprofezin against mealy bug in cotton. The efficacy of buprofezin against P. solenopsis on cotton was found to be dose dependent. Buprofezin at all the three doses was more effective followed by carbaryl and chlorpyriphos. There was more than 95 per cent reduction in mealy bug population over control after 3 DAS in buprofezin at all the three doses. In case of carbaryl and chlorpyriphos the per cent reduction was less than 70. Buprofezin was more effective at two higher doses (312.5 and 625 g a. i. /ha) compared to its lowest dose (250 g a. i. /ha). The efficacy of buprofezin against early and later instar nymphs of P. solenopsis under laboratory condition was also found to be dose dependent. It was more toxic to early instars than later instar nymphs. It was most effective against early as well as later instars nymphs at highest dose (625 g a. i. /ha). At 2 lower doses (250 g a. i. /ha and 312.5 g a. i./ha), its effectiveness was comparable to chlorpyriphos 400 g a. i. /ha and Carbaryl 1000 g a. i. /ha.