The effects of crude extracts of leaves of Ocimum sanctum (OSL) Catharanthus roseus (CRL) Acalypha indiaca (AIL) and Vitex negundo (VNL) at four different concentrations were observed in the IV instar larvae of Culex quinquefasciatus, a vector of filariasis. The two higher concentrations viz. 750 and 1000 ppm of Vitex negundo leaf extracts resulted in 86.67% mortality in the IVth instar larvae of C. quinquefasciatus. The order of effect of leaf extracts is VNL< CRL < OSL< AIL. The order of percent mortality in VNL, CRL, OSL and AIL is 86.67, 80.00, 46.67 and 46.67% respectively in 1000 ppm. In lower concentrations ( 250 and 500 ppm), there is no mortality due to the leaf extracts of OSL and AIL, whereas the leaf extracts of Vitex negundo and Catharanthus roseus leaf extracts have more potential effect over C.quinquefasciatus than the leaf extracts of other two plants viz., plants Ocimum sanctum and Acalypha indiaca.