Five lines of tetraploid wheat (T. turgidum dicoccoides) from 2 contrasting wild habitats in Israel, and 2 hexaploid wheat (T. aestivum vulgare) cultivars, one of spring habit and the other winter habit, were compared for responses to vernalization and photoperiod. The responses of the T. t. dicoccoides lines were within the ranges observed for the hexaploid cultivars. There were differences in the levels of responses of the T. t. dicoccoides lines from the 2 habitats, those from the habitat with the shorter growing season (Bet Shean Valley) having generally lower levels of vernalization and photoperiod response than those from habitat with the longer growing season (Mt. Hermon Slopes). These differences indicate the occurrence of genetic differentiation amongst wild populations of this species for developmental responses. It appears that the spring habit of T. t. dicoccoides arose from winter habit forms. Within-population differences were also observed for these characters, indicating that the wild population of T. t. dicoccoides is most likely to be genetically polymorphic for developmental responses.