The developmental rate and frost tolerance of flower buds of 20 apricot varieties were studied during winter. Cluster analysis was carried out on the matrices of these data to establish the different adaptation types. The varieties were placed in four groups. Three varieties belonged to the first group with the best winter hardiness, and the longest endodormancy, 'Zard' of Central-Asian origin, and the two interspecific hybrids, 'Plumcot' and 'M 604'. The varieties in the second groups have good frost tolerance during endodormancy, and their frost tolerance decreases relatively slowly during early spring. To this group belong 'Bergeron', 'Harlayne', 'Harglow', 'Hargrand' and 'Veecot'. The endodormancy of the varieties belonging to the third group was rather short, after which their frost tolerance decreases rapidly. 'Gönci magyar kajszi' that has excellent fruit quality belongs to this group. The varieties in the fourth group possess the worst winter hardiness and very short endodormancy. To this group belong 'Cafona' and Tracasso' of Mediterranean origin, 'Ceglédi bíborkajszi', 'Ceglédi órias' and 'Harmat' of the Hungarian varieties.