Aim. Comparative analysis of the traits of the assimilation surface of winter wheat varieties under unfavorable environmental conditions to evaluate its adaptive capacity. Methods. Morphometric, spectrophotometric, statistical. Results. In the field experiments under natural conditions (close to optimal in spring, arid - during the grain filling period and prolonged rainfall during a harvest), the variability of leaves chlorophyll content, the green leaves fresh matter per 1 m2 of ground and chlorophyll index in 10 modern middle-early varieties at anthesis and milky-wax ripeness were studied. Under such conditions, the difference in grain productivity between the highest and the lowest yielding varieties was about 1.6 t/ha. Positive correlation of grain productivity of winter wheat varieties with chlorophyll area index of leaves at milky-wax ripeness (r = 0.61) was established. Conclusions. It was found that the varieties with better adaptation to drought conditions during the period of grain filling had a higher area of assimilation surface at anthesis and milky-wax ripeness. Therefore, their higher yield was related to the higher photosynthetic capacity and the ability to storage and remobilization of carbohydrates deposited in the stem as well as to the efficiency of converting total biomass into grain yield (HI). Keywords: Triticum aestivum L., grain productivity, chlorophyll area index of leaves.