The article provides the analysis of the maintenance stability of genetic structure of generatively young and middle-aged trees in seed progenies formed during two years in Donbass population of Pinus sylvestris var. cretacea Kalenicz. ex Kom. protected in Ukraine. The analysis has been carried out at 10 allozyme loci. Allele and genotype diversity of the trees is reproduced annually in seed progenies in spite of the low values of outcrossing coefficient (ts=0,371–0,687; tm=0,731–0,790) and significant excess of homozygotes in the embryos. Genetic structure fluctuations are observed in embryos and in the pool of paternal gametes in seed progenies of different years.