To determine whether or not a new 3 cm long angioplasty balloon was more effective in treatment of long (15-25 mm) or tandem (< 25 mm overall length) coronary lesions, 44 consecutive patients with suitable lesions were alternately assigned to treatment with shorter, standard, 2 cm length, or long, 3 cm balloons. Primary success of PTCA was achieved in 95%. Those treated with long balloons required fewer inflations (3.3 +/- 1.5 vs. 5.7 +/- 2.1, P = .0001) and showed fewer moderate or severe intimal dissections of the lesions (4/22 vs. 12/22, p = .028.) The use of 3 cm PTCA balloons in long or tandem lesions appears to be efficacious and less likely to cause dissections than shorter, 2 cm length devices.