On basis of agrophenological observations from 27 experiment stations for cultivar assessment COBORU (Research Centre For Cultivar Testing), which consisted of dates of potato planting, emergence, flowering, haulm drying, harvest, established for the medium early potato standard, the variability in time and space of the agrophenological stages of that plant in Poland was assessed. The dependence of the interphases duration of potato on temperature and precipitation in the years 1972-1995 was also assessed. In Poland, the difference in the appearance of potato growth stages in various parts of the country is almost 3 weeks. The greatest differences (over 3 weeks) pertain to the time of seeding, the smallest (about 2 weeks) time of haulm drying and harvest. The duration of interphases of medium early potato can be described by agrometeorological factors and time of the beginning of the interphase from 32.7 to 59.3%, the poorest description pertaining to the duration of interphase emergence-flowering, the best � interphase flowering-haulm drying.