Interspecific crosses between the cultivated soybean, Glycine max (L.) Merr., and the wild species. Glycine soja Sieb. & Zuce, may be useful for broadening the genetic base of commercial cultivars. The objectives of the study were to evaluate agronomic traits of G. max, G. soja and their F1 hybrids in tropical and temperate environments, to determine whether cytoplasmic effects were present for agronomic traits and seed composition in reciprocal crosses between the two species, and to evaluate the type of gene action that controls the inheritance of traits in interspecific crosses. Reciprocal crosses were made between 'Century' and PI326581 and between 'Amsoy 71' and PI424001. Thirty plants of each of the parents and 50 F1 plants of each cross were grown at two environments in Puerto Rico and one in Iowa. The traits evaluated were date of stages R1 and R8, leaf size, shattering, defoliation, vining, lodging, agronomic type, plant height, 100-seed weight, percentage of seed protein and oil, and percentages of palmitic, stearic, oleic, linoleic, and linolenic acids in the oil. No significant differences were observed among environments for seven of the 11 agronomic traits evaluated in the two crosses. The relative performance among genotypes for all traits in Iowa and Puerto Rico was similar. This similarity indicates that it is possible to use tropical locations to evaluate the progeny of interspecific crosses. No significant differences between F1 plants of reciprocal crosses were observed in the two crosses for any of the traits; thus, cytoplasmic effects were not important. The type of gene action observed differed among traits and included additive, dominance, and partial dominance.