BACKGROUND. In myeloid blasts, the expression and release of the multifunctional chemokine IL-8 could be expected to be differentiation-associated. METHODS. We investigated the profile of interleukin-8 (IL-8) expression and release by leukemic cells obtained at diagnosis from 42 untreated adult patients with acute myeloid leukemia of various FAB subtypes (2 M0, 7 M1, 6 M2, 6 M3, 10 M4 and 11 M5). IL-8 transcripts were evaluated by Northern blot and densitometric analysis. IL-8 release by myeloid blasts was evaluated by a specific ELISA either in sera at diagnosis or in supernatants (SN) obtained from cultured leukemic cells. RESULTS. In basal conditions, Northern blot analysis revealed detectable IL-8 transcripts in 15/29 cases, eleven of which were classified as M4-M5 and 4 as FAB M0-M3. Densitometric analysis of IL-8 transcript bands showed higher expression in M4-M5 than in M0-M3 cases (mean values +/- SD: 16.5 +/- 21 and 0.77 +/- 1.36 densitometric units, respectively; p = 0.012). Higher IL-8 serum le