325 coronary lesions in 300 consecutive patients (257 male, 43 female, 52 +/- 8 years) undergoing either single-vessel (n = 275) or double-vessel PTCA in two independent procedures (n = 25) were prospectively randomized to either one (group A, n = 167) or three (group B, n = 168) balloon inflations. By clinical and angiographic criteria, PTCA was successful in 295/325 lesions (90.8%) with no significant difference for group A (88.6%) and B (93.0%). Clinical followup was achieved in 92% of patients and angiographic followup was obtained in 261/295 (88.5%) successfully dilated lesions (A: 87.8%; B: 89.1%). Angiographic appearance of the dilated lesion (in % diameter stenosis) prior to PTCA, directly following PTCA and at follow-up was comparable for both groups: gr. A: 71 +/- 11%, 32 +/- 10%, and 40 +/- 21%; gr. B: 70 +/- 11%, 30 +/- 10%, and 40 +/- 20% resp. Restenosis rate was similar with 26.9% in group A and 29.8% in group B. The randomization had to be abandoned in 144/325 cases (44.3%) due to medical reasons. Results of only those lesions where it was possible to follow the initial randomization demonstrated a different pattern. Success rate was slightly higher in those with 3 inflations (gr. B1, n = 111) with 93.0% as compared to lesions with only one inflation (gr. A1, n = 70) with 88.6% success (p = ns). Subsequently, the initial angiographic result was slightly better for B1 with a reduction in diameter stenosis from 69 +/- 11% to 29 +/- 10% compared to A1 (71 +/- 11% and 32 +/- 10% resp.). But at follow-up the initial greater gain was lost in B1 with an increase of diameter stenosis to 41 +/- 19% (p < 0.05 vs post PTCA) and a restenosis rate of 30.5%. In group A1, diameter stenosis at follwow-up increased slightly to 36 +/- 19% (p = ns vs post PTCA) with a restenosis rate of 15.5% (p < 0.05 vs B1). Conclusions: A single balloon inflation during elective PTCA results in a low restenosis rate and an excellent angiographic long-term result if the first inflation leads to a sufficient reduction in diameter stenosis with no clinical complications during hospital stay. Multiple balloon inflations demonstrate a slightly better initial angiographic result but are associated with a higher restenosis rate at follow-up and worse angiographic outcome.