Percutaneous transluminal renal angioplasty has been shown to be an effective technique to dilate renal artery lesions, particularly those due to fibromuscular dysplasia. However, four of 70 patients in this study experienced atypical responses to angioplasty. Their lesions initially resisted dilation and had incomplete dilatation immediately after angioplasty. Long-term follow-up (1 week to 2 years) angiograms, however, demonstrated fully dilated arteries. In cases of focal nonatherosclerotic lesions from intimal or adventitial fibroplasia, initial incomplete dilatation may be satisfactory in the long term whereas repeated inflations may result in undesirable complications.