While in normal individuals all these molecules are broadly expressed on leukocytes, in patients with leukemias the following deviations were observed: (a) at least one of the examined molecules was missing in 64/68 cases (94%); in 12/68 cases (18%) both molecules LFA-1 and ICAM-1 were missing, in 37/68 (54%) either LFA-1 or ICAM-1, and in 15/68 cases (22%) adhesion molecules other than LFA-1 or ICAM-1 were missing; (b) the expression of CD11a/CE18, CD58, CD59 on leukemic cells was heterogeneous, without any clear correlation to the subclass of leukemia; (c) in the majority of cases, CD54 (45/68; 66%) and CD44 (36/68; 53%) were missing, however showing a tendency of expression on leukemic cells with more mature immunophenotype.