The distribution of ADA activity has been studied for ADA 1 and ADA 2-1 individuals in intact and lysed erythrocytes and in lymphocyte lysates. ADA activity in intact RBC is 20-30% lower than in lysates, in lymphocytes it is 10 times higher. The difference between ADA 1 and ADA 2-1 mean enzyme activities which we previously described in RBC lysates has been found also in intact RBC and in lymphocyte lysates.