Soybean looper, Pseudoplusia includens (Walker), oviposition in cotton, Gossypium hirsutum L., and soybean, Glycine max (L.) Merr., of various stages of plant phenological development was evaluated in field cages in 1994, 1995, and 1996. Overall, females preferred to oviposit on soybean over cotton when both crops were compared in vegetative or prebloom stages, when both crops were blooming, and when soybean was blooming or in early pod stage compared with prebloom cotton. Females preferred to deposit eggs on the lower leaf surface in the upper two-thirds of the plant canopy in cotton and soybean. Oviposition in upper and middle canopy levels varied with plant growth stage. Females tended to lay more eggs in the upper canopy compared with the middle canopy in prebloom cotton and vegetative soybean; more eggs were laid in the middle canopy of blooming cotton and reproductive stages of soybean. Females responded to both cotton and soybean volatiles in an olfactometer. There was no significant difference in response to the two sources of volatiles.