According to previously reported data, the supernatant of a primary culture of human erythrocytes contains 33 hemoglobin fragments. An analysis of the supernatant of a 20% (v/v) suspension of human erythrocytes allowed us to identify additionally four peptides whose precursors are cytoplasmic beta-actin (two fragments), fructose diphosphate aldolase B, and an unknown protein, as well as the amino acids tyrosine and tryptophan. The composition and the content of the components of the supernatant did not depend on the age or blood group of donors. The dynamics of accumulation in the supernatant (20-80 min of incubation) of the 14 hemoglobin fragments with the most reliably reproducible contents was obtained. The content of six peptides increased more than twofold between 20 and 40 min of incubation: the maximum increase in concentration was observed between 40 and 80 min (140%). The level of peptides that had the maximum concentration at the end of incubation was about 1000 pmol/ml of sedimented erythrocytes. The biological effects of the peptides identified in the supernatant of erythrocytes involve the stimulation of proliferation and hemopoiesis, suppression of proliferation, a bactericide effect, etc. These effects indicate the physiological importance of peptide release by erythrocytes. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.