Studies were carried out to evaluate the larvicidal, growth inhibitor and repellent actions of D. sissoo oil against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus under laboratory conditions. Pure oil was applied at 0.4-5 ml/m(2) on a water surface. This showed that larvicidal activity was directly proportional to dosages. One hundred percent mortality of Ck. quinquefasciatus immatures was observed within 24 h at 4 ml/m(2), followed by Ae. aegypti (90%) and An. stephensi (60%), and pupation was totally inhibited. Adults which emerged from exposure to a sublethal dosage (2 ml/m(2)) either did not lay eggs (Ae. aegypti) or hatch (Cx. quinquefasciatus and An. stephensi). The oil also showed strong repellent action when 1 ml oil was applied on exposed parts of human volunteers. They were protected from mosquito bites for 8-11 h. The protection (91.6 +/- 2%) obtained with sissoo oil was comparable to that with commercial Mylol oil (93.8 +/- 1.2%) consisting of di-butyl and dimethyl phthalates.