The center‐of‐origin cottons (Gossypium spp.) are isolated from cultivated American cottons by their shortday flowering response, and an understandng of the inheritance of flowering response is important hi attempting to transfer genes from these primitive cottons. The genetic systems controlling flowering response in Gossypium hirsutum and G. barbadense cottons were studied in diallel crosses involving short‐day anl day‐neutral lines of each species. The G. hirsutum lines were Texas Marker‐1 and M‐ll (day‐neutral) and Texas 220 and Texas 371 (short‐day). The G. barbadense lines were ‘Pima S‐l’ and 3‐79 (day‐neutral) and ‘Lengupa’ (shortday). These lines were crossed in all possible combinations, and the F1, F2, backcrosses to both parents, and a testcross to Texas Marker‐1 were grown for each combination. Flowering response was recorded as percentage of flowering plants and the mean date of flowering for each line in the field at College Station, Texas. A failure to meet the preanalysis tests of assumptions prevented the analysis of these data by the Hayman‐Jinks diallel analysis. The data were analyzed by comparison of mean, performance. We concluded that G. hirsutum and G. barbadense, represented in this study, have nonhomologous systems controlling flowering response. Within G. barbadense, flowering response is recessive to nonflowering and under single‐gene control. In G. hirsutum, however, flowering response is under multigenic control, which is partially dominant or additive to nonflowering. In interspecific cross combinations, the segregation for flowering response follows a multigenic pattern.