ABSTRACT Considering the prevention of crop production, aimed at adaptation to climate changes, searching for or developing genotypes resistant to water deficit is a challenge for modern agriculture and a strategic goal of plant breeding. The objective of the study was to determine the effect of drought stress on the vigor of naked and husked oat (Avena sativa L.) cultivars. The studies concerned eight naked oat cultivars and two husked oat cultivars characterized by high germination capacity (above 95%). Seeds of naked oat cultivars showed susceptibility to varied thermal conditions during drought simulated by the use of polyethylene glycol (PEG) at a concentration of -1.5 MPa. An increase in temperature from 10 to 20 °C resulted in an average 37% increase in the number of normally germinating seeds, and in a more than 40% increase in germination rate, as well as in a 25% decrease in average germination time. A distinct increase in osmotic potential from -1 to -2 MPa during drought stress induction resulted in 15% decrease in vigor of husked cultivars measured by the percentage of normally developed seedlings. The vigor of oat cultivars, evaluated on the basis of electrical conductivity of exudates, was modified by genotypic variability. In naked cultivars, on average, 60% lower values were noted. The coefficients of correlation between electrical conductivity of exudates and germination capacity (r = -0.784**) or frequency of normally developed seedlings (r = -0.919**) confirm the highly significant interrelationship between the methods used for the evaluation of oat seeds under drought conditions.