Hrenovskoy pine forest is a unique island stand at the boundary of the species range of Scots pine Pinus sylvestris L. This object is of exceptional economic value, because it serves as a forest-seed base for the Voronezh oblast and some other regions of Russia; therefore, the stand and seed qualities have to be monitored constantly. The results of the first cytogenetic study of the seed progeny of P. sylvestris from the Morozov Grove, a high-quality stand in a reserved site within the Hrenovskoy pine forest, are reported. The studies have been performed in order to obtain a more correct assessment of seed quality based not only on their germination and energy of germination (traditionally used by forest breeders), but also on their genomic stability. The latter may be estimated by the stability of chromosome number in the somatic cells of seedlings and the regularity of mitotic divisions, because they also characterize the state of the generative system of parental forms and may serve as an integrated estimate of the stand development homeostasis. Therefore, the chromosome number, mitotic and nucleolar activities, and the number and spectrum of pathological mitoses (PMs) have been determined. Seedlings have been obtained from 240 seeds (collected from 12 trees) that resulted from free pollination. The cytological analysis of the rootlets of these seedlings has not detected any deviations from the chromosome number typical of the species P. sylvestris L. (2n = 24). However, considerable variation has been found in each family with respect to the mitotic index (MI) (from 4.2 +/- 0.36 to 8.1 +/- 0.39%) and the number of PMs (from 0.5 to 2.1%); micronuclei have also been found in each family (from 0.01 to 0.05%). In general, the phenotypic characteristics and the variation pattern of cytological parameters of the progeny of the trees studied in the Hrenovskoy pine forest, together with the high germination rate of seeds (90-98%), indicate that the current state of pines in the Hrenovskoy pine forest can be considered to be satisfactory. However, the presence of micronuclei in all variants and the decrease in MI in some individual plants (which was, on average, 6.1 +/- 0.03% in the sample studied, i.e., significantly lower than that of P. sylvestris from the Usmanskii pine forest (7.3 +/- 1.2%), where the conditions are optimal for this species) may serve as the bioindicators of the deterioration of both the state of trees themselves and the ecological conditions in the Hrenovskoy pine forest. Therefore, the population structure of this valuable autochtonic stand should be reproduced urgently.