In twenty patients with unstable angina, the effects of percutaneous transluminal coronary angioplasty (PTCA) on superoxide anion generation by neutrophils (PMNs) obtained from ulnar vein (UV) and coronary sinus (CS) were investigated. Blood samples for the investigations were taken from CS just before the procedure, within the first minute after the last balloon inflation and 20 minutes after PTCA; from BV--just before the procedure and 20 minutes following it. The results were compared with those obtained from 12 patients with unstable angina, (in whom coronary angiography was performed, but for various reasons angioplasty was desisted from) and with those obtained from 20 clinically healthy persons. In patients with unstable angina, the significantly increased O2.- generation by PMNs from CS and BV was found at rest as well as following opsonized-zymosan stimulation, compared with healthy persons. Within the first minute after PTCA, the significantly decreased O2.- generation by PMNs from CS was observed, compared with the results before the procedure (rest.--11.29 +/- 0.73 and 10.15 +/- 0.65 nmol/cell/min., p < 0.05; stimulation--27.62 +/- 6.25 and 18.54 +/- 3.37 nmol/cell/min., p < 0.05). Twenty minutes after PTCA O2.- generation by PMNs from CS still decreased (rest--9.23 +/- 1.08 nmol/cell/min., stimulation--15.71 +/- 5.98 nmol/cell/min.). In blood samples taken from BV before and after PTCA, no statistically significant differences in O2.- generation were observed (rest--11.32 +/- 0.79 nmol/cell/min. and 10.77 +/- 1.43 nmol/cell/min.; stimulation--25.96 +/- 6.12 nmol/cell/min. and 21.15 +/- 5.47 nmol/cell/min.).