We performed percutaneous coronary angioscopy in 35 patients to study the surface morphology of coronary artery lesions. Twenty‐five patients had angioscopy performed in conjunction with PTCA, including 20 patients with de novo lesions (16 patients with unstable angina, four patients with stable angina), and five patients with restenosis lesions. Ten cardiac transplant patients had angioscopy performed in conjunction with annual follow‐up angiography in an attempt to identify accelerated atherosclerotic lesions. There were no complications of angioscopy in any patient. There were no intracoronary thrombi seen either by angiography or angioscopy in the stable angina patients. In the unstable angina group, angiography identified thrombus in 2 out of 16 (12.5%) versus 15 out of 16 (94%) (P<0.001) with angioscopy. Following angioplasty, dissections were seen angiographically in 7 out of 16 (44%) of patients versus 16 of 16 (100%) of the patients by angioscopy (P<0.01). Restenosis lesions were characterized by a white, fibrous appearance instead of the usual yellow color of primary atherosclerotic lesions. In the ten cardiac transplant patients, angioscopy appeared to be more sensitive than angiography for the detection of atherosclerosis. Yellow (atherosclerotic) and white (fibrotic) plaques were seen in the transplant patients, which often were not detected by angiography. In summary, angioscopy is an excellent tool for visualizing the surface morphology of coronary artery lesions. The clinical indications for angioscopy remain undefined at present. Possible applications for angioscopy include intracoronary thrombolytic therapy, stratification of high risk angiographic results after angioplasty (“hazy” artery), and, finally, as an adjunct to interventional procedures such as stem impla