In a series of laboratory oviposition assays, gravid Toxorhynchites splendens exhibited a preference for cups containing Aedes aegypti larval rearing water, but not for cups containing liquid cultures of bacteria, live Ae. aegypti in distilled water, Ae. aegypti larval holding water with reduced bacterial contamination, or methyl propionate at 0.1, 0.2 and 0.3% in distilled water. Preoviposition flight behavior was elicited by dark-colored containers, but few eggs were deposited if they contained no water. An invisible source of humidity placed in cups enhanced oviposition, but a reflective surface placed in dry cups did not. It is concluded that this species is strongly influenced by humidity and visual stimuli in the acceptance of a site for oviposition.