The relationship between percentage of empty seed (Pes) and genetic factors was explored in an isolated stand of European beech (Fagus sylvatica L.). Nine allozyme loci (GOT-B, IDH-A, LAP-A, MDH-B, MDH-C, MNR-A, 6-PGDH-A, PGI-B and PGM-A) were used to estimate genetic factors. Pes ranged from 4.8% to 40.9% for seed samples of 91 trees within the stand and showed an approximate normal distribution. The average Pes was 21.4% and the repeatability of Pes was 43.4%. The multilocus estimate for outcrossing rate (t m ) based on seed samples of 30 trees within the stand was 1.015(SE = 0.011) and the mean single locus estimate was slight higher at 1.061(SE = 0.026). No evidence of biparental inbreeding was found. Weak positive correlation between Pes and maximum selfi ng rate as well as and signifi cant negative correlation between Pes and multilocus outcrossing rate indicated that self-fertilization may be explained as one of the important causes of empty seeds in beech.