Changes in the content and composition of fatty acids in phospholipids were determined to estimate the effect of propranolol on the growth of unicellular green algae Chlorella vulgaris cultivated synchronously. The general biological activity of the cells and the division coefficient (DC) as well as the cell synchronisation were disturbed by propranolol in a concentration dependent manner. Also, the effect of propranolol on the fatty acids content of Chlorella vulgaris phospholipids was proportional to its concentration.