<jats:title>Abstract</jats:title><jats:p>A crude chloroform extract of seeds of <jats:italic>Millettia dura</jats:italic> Dunn (Leguminosae) showed high activity (LC<jats:sub>50</jats:sub> = 3.5 µg ml<jats:sup>−1</jats:sup> at 24 h) against second‐instar larvae of the mosquito, <jats:italic>Aedes aegypti</jats:italic> L (Diptera: Culicidae). The rotenoids, deguelin and tephrosin, isolated from the seeds of this plant also showed potent activities, with LC<jats:sub>50</jats:sub> values of 1.6 and 1.4 µg ml<jats:sup>−1</jats:sup> at 24 h, respectively. The related rotenoids millettone and millettosin were inactive at 20 µg ml<jats:sup>−1</jats:sup>. Saturation at the B/C ring junction and the presence of methoxy groups at C‐2 and/or C‐3 in deguelin and tephrosin appear to be important for the observed larvicidal activity. Copyright © 2003 Society of Chemical Industry