Lower aliphatic carboxylic acids are known to induce negative ovipositional responses in various species of mosquitoes. Straight-chain higher fatty acids from C5to C13and some of their methyl and ethyl esters and amides were evaluated for ovipositional activity in a laboratory olfactometer system against two species ofCulexand one species ofAedesmosquitoes. Of these higher acids, nonanoic acid (C9) was the most repellent againstC. quinquefasciatusandC. tarsalis, demonstrating significant repellency at 1 × 10−4M. Nonanoic acid was also the most active acid againstA. aegypti, significantly repelling the ovipositing mosquito at as low as 1 × 10−5M. Some of the higher acids, such as C8, C9, and C10acids, were as active as, or more active than, the lower acids from C2to C6against these three species of mosquitoes. Among the methyl and ethyl esters of C8to C10acids, only ethyl nonanoate showed considerable repellency. The amides of C8to C10acids did not exhibit any activity.