The main problem of the Hungarian apricot production is frost injury during the winter and early spring. We need varieties with higher cold hardiness. Scientists are looking for an appropriate basis for freezing tolerance but it is rather difficult, because the background of cold hardiness and dormancy of temperate zone fruit trees is not understood sufficiently. In our work we tried to find relationship between dormancy markers and cold hardiness of flower buds. We have studied four traditional Hungarian apricot varieties (Ceglédi bíbor, Ceglédi óriás, Gönci magyar kajszi and Mandulakajszi) during three years. Blooming under forcing was observed. Microsporogenesis was registered using microscope. Frost tolerance of flower buds was determined by artificial freezing in laboratory freezing chamber and changes of LT50 values were calculated during winter. According to our results there is no relation between blooming rate under forcing and the changes in cold hardiness. We could find a significant relation between stages of microsporogenesis and rate of cold hardiness. Flower buds lost their cold hardiness as soon as the meiosis started. Study of microsporogenesis seems to be a useful method in the selection for a long rest period in apricot.