CASHEW nut (Anacardium occidentale Linn.) shell liquid obtained from unroasted shells was found by Stadeler1 to consist chiefly of anacardic acid (A) (on heating, this is decarboxylated to cardanol (B)), a salicylic acid derivative with a long unsaturated side-chain in the position ortho to the carboxyl group, and cardol (C), a resorcinol derivative with a similar side-chain. Smith2 showed that the unbranched side-chain consisted of 15 carbon atoms and 2 double bonds ; other workers3 have shown that the oily liquid is really a mixture of saturated and mono-, di-, and tri-olefinic compounds in proportions that give, on average, about two double bonds per molecule. Although the surface-active properties of the sulphonated shell liquid have already been studied4, no thorough investigation has yet been carried out on anacardic acid, which, being an arylalkyl surfactant and a promising bactericidal agent, needs special attention5. Results of a preliminary study on sodium anacardate as a surfactant and bactericidal agent are reported here. .