Among 356 consecutive patients with successful TCA performed between October 1977 and June 1983 follow-up angiograms were performed in 333 patients (94%). A total of 439 follow-up angiograms at 1-48 (average 5.6) months after successful angioplasty were analysed. Restenosis rate was 12% if defined as remaining widening of less than 20% compared with the situation before angioplasty. It was 16% if defined as loss of at least half of the initial gain in luminal diameter, and 17% if defined as increase from immediate post-TCA-stenosis of much greater than 30% or the loss of at least half of the initial gain in luminal diameter. This value dropped to 15% if the subgroup of 30 patients with second TCA and of 14 patients with dilatation of an aortocoronary bypass stenosis were excluded; in both subgroups recurrence rate was higher (33% and 45%, respectively). The observed restenosis rate is less than 50% of that reported by the PTCA registry of the NHLBI. Several factors can possibly be responsible for the reduction in restenosis rate: selection of patients; technique of TCA; medical treatment during and after TCA; modification of risk factors, compliance of patients; unknown factors. Long-term medical treatment with acetyl salicylic acid, nitrates and calcium blockers in high doses is considered to be most probably responsible for the favourable results.