The activity levels of the enzyme poly(A)polymerase and the levels of protein synthesis primed by endogenous messenger RNA (mRNA) as well as polyuridylic acid, poly(U) directed polyphenylalanine synthesis, were determined in lymphocytic extracts from 17 patients with chronic lymphocytic leukemia of the B cell type. The enzyme activity values have not been found to correlate with the poly(U)-protein synthesis, whereas a positive linear correlation has been established between the activity levels of poly(A)polymerase and the endogenous mRNA-primed protein synthesis (r = 0.735, p less than 0.01). This difference between exogenously and endogenously primed protein synthesis in concern with poly(A)polymerase is discussed.