Neutrophil superoxide anion (O(2)(*-)) generation was measured during carvedilol therapy in patients with stable angina. The carvedilol group comprised 27 patients (18 men and 9 women), aged 38-51 years (mean 47.6 years) with stable angina. Carvedilol was administered in increased every 4-week doses: 12.5, 25 and 50 mg/24 h, respectively. The control group included 12 healthy subjects, aged 39-49 years (mean 45.7 years) with no drug administered. Blood samples were collected from cubital vein before and 4, 8 and 12 weeks after the therapy and once in the control group. Neutrophil O(2)(*-) generation was determined in whole blood without and with opsonized zymosan (OZ) stimulation according to Bellavite et al. method using superoxide dismutase from bovine erythrocytes. O(2)(*-) generation by nonstimulated and OZ-stimulated neutrophils was significantly higher (p<0.05) in patients with stable angina than in the control group. In carvedilol group, statistically significant (p<0.05) decrease in superoxide anion generation by nonstimulated and OZ-stimulated neutrophils was observed 8 and 12 weeks after the therapy and it did not differ from that in healthy subjects. Carvedilol has been shown to inhibit neutrophil O(2)(*-) generation in patients with stable angina.