Objective:To determine the larvicidal and adult emergence inhibition activities of castor (Ricinus communis) seed extract against three potential mosquito vectors Anopheles stephensi(An. slephensi),Culex quinquefasciatus(Cx.quinquefasciatus) and Aedes albopictus(Ae.albopictus) in India.Methods:The R.communis seed extract was tested,employing WHO procedure,against fourth larval instars of the three mosquito species for 24 h and larval mortalities were recorded at various concentrations(2-64μg/mL):the 24 h LC_(50) values of the R.communis seed extract were determined following Probit analysis.The larval killing,antipupation and adult emergence inhibition rates of the test extract,using a single concentration of 2μLC_(50),were studied at different time periods(24-72 h):the extract toxicity was tested against a fish.Oreochromis niloticus(O.niloticus).Results:The R.communis seed extract exhibited larvicidal effects with 100%killing activities at concentrations 32-64μg/mL,and with LC_(50) values 7.10.11.64 and 16.84μg/mL for Cx.quinquefasciatus,An.stephensi and Ae.albopictus larvae,respectively. When the larvae were treated with the extract at a single concentration of 2×LC_(50),significant differences were observed,compared to control groups,in rate of pupation(P<0.001) as well as in adult formation(P<0.001).Conclusions:The present findings suggest that the R.communis seed extract provided an excellent potential for controlling An.stephensi,Cx.quinquefasciatus and Ae. albopictus mosquito vectors. Objective: To determine the larvicidal and adult emergence inhibition activities of castor (Ricinus communis) seed extract against three potential mosquito vectors Anopheles stephensi (An. Slephensi), Culex quinquefasciatus (Cx.quinquefasciatus) and Aedes albopictus (Ae. Albopictus) in India. Methods: The R.communis seed extract was tested, to WHO procedure, against fourth larval instars of the three mosquito species for 24 h and larval mortalities were recorded at various concentrations (2-64 μg / mL): the 24 h LC - (50) values ​​of the R.communis seed extract were determined following Probit analysis. The larval killing, antipupation and adult emergence inhibition rates of the test extract, using a single concentration of 2μLC_ (50), were studied at different time periods (24-72 h Results: The R.communis seed extract exhibited larvicidal effects with 100% killing activities at concentrations 32-64 μg / mL, and with LC_ (50) values ​​7.10.11.64 and 16.84 μg / mL for Cx.quinquefasciatus, An.stephensi and Ae. albopictus larvae, respectively. When the larvae were treated with the extract at a single concentration of 2 × LC_ (50), significant differences were observed, compared to control groups, in the rate of pupation (P <0.001) as well as in adult formation (P <0.001) .Conclusions: The present findings suggest that the R.communis seed extract provided an excellent potential for controlling An.stephensi, Cx .quinquefasciatus and Ae. albopictus mosquito vectors.