The expression of myelomonocytic (My+) associated antigens on lymphocytes from B-chronic lymphocytic leukemia (B-CLL) was studied in 62 patients. Most of them expressed at least a My(+) antigen: CD11b in 40 cases (64.2%), CD13 in 31 (50%), CD14 in 18 (29%), CD33 in 41 (66%), CD36 in 6 (9.6%). The relationship between the clinical features of the disease and My(+) antigen status was studied. No significant correlation was found between Rai's clinical stages and the average percent value of CD11b, CD13, CD33 and CD36. In contrast, patients in Rai's stage 0 had a significant lower value of CD14 positive cells than those with more advanced disease (P < 0.001). Interestingly, patients with a diffuse bone marrow histology had a higher average percent value of CD33-positive cells (76.3% ± 29.3) than those with a non-diffuse one (50.4% ± 37.5). Furthermore, 90% of My(-) patients fulfilled Montserrat's criteria of "smouldering" CLL while only 48.3% of My(+) cases did (P < 002). My(+) lineage antigens on B-CLL cells may provide another criterion to characterize patient subgroups with a poor prognosis.