Three wheat (Triticum aestivum L.) mutants that lacked dormancy at maturity were isolated from an ethylmethane sulphonate-treated population of a dormant red-grained line, Kitakei-1354 (Kitakei). The three mutants (EH47-1, EH47-2-5 and EH47-2-6) were selected in segregating generations derived from one M2 plant. They differ in morphological and physiological characteristics, showing that these mutants contained several mutations besides non-dormancy. Despite these differences, embryos of all the mutants rapidly lost sensitivity to abscisic acid (ABA) during the later half of seed maturation while Kitakei embryos maintained the sensitivity even after maturity. These results suggest that embryo sensitivity to ABA plays a key role in seed dormancy. The profile of ABA content of EH47-1 embryos during seed development was similar to that of Kitakei, except for a significantly lower level at 30 d after pollination (DAP). This reduced level of ABA at DAP30 is discussed in relation to the development of seed dormancy and ABA sensitivity of the embryos. Segregation ratios for non-dormancy in progeny of EH47-1×Kitakei crosses suggest that the non-dormancy of EH47-1 is a single dominant mutation.