Ovipositing Aedes aegypti (L.) females were attracted to waters in which uninfected Aedes atropalpus (Coquillett) larvae had been reared, but were repelled by waters from larvae of either species infected with the entomopathogenic digenean Plagiorchis elegans (Rudolphi). In contrast, Ae. atropalpus females were attracted to or repelled by waters from conspecific uninfected and infected larvae, respectively, but did not respond to corresponding waters from Ae. aegypti larvae. The sensitivity of ovipositing females of both species to repellents and attractants is discussed in terms of possible selective pressures exerted by unstable breeding environments.