Various regimes of freezing and thawing as well as adrenaline and fluoride ions are studied for their effect on the adenylate cyclase activity in liver tissue preparations. The reduction of basal and fluoride-stimulating adenylate cyclase activity and a decrease in the adrenaline-stimulating activity of the enzyme after freezing and thawing are shown. Freezing and thawing are studied for molecular mechanisms of their damaging effect on adenylate cyclase.