To determine whether radiofrequency ablation for supraventricular tachycardia causes significant minor myocardial injury, 16 patients with supraventricular tachycardia undergoing radiofrequency ablation were studied. Cardiac troponin T, creatine kinase and its MB form (CKMB) were measured before, immediately after ablation and every 6 h thereafter for 24 h to detect myocardial injury. Elevation of creatine kinase, CKMB and cardiac troponin T was observed in 6, 4 and 5 patients, respectively. The peak mean creatine kinase concentration was 167 ± 152 IU/1 and that of CKMB was 9 ± 6 IU/1. The peak mean cardiac troponin T level was 0.44 ± 0.47 ng/ml. The frequency of elevated measurements was not statistically different among creatine kinase, CKMB and cardiac troponin T. The mean pulse numbers of ablation, mean duration of ablation, radiofrequency current and mean total energy did not differ statistically between those with or without elevated cardiac troponin T. It was concluded that radiofrequency ablation for supraventricular tachycardia indeed caused some minor myocardial injury and the frequency of elevated cardiac troponin T was comparable to that of CKMB.