Angiographic evidence of coronary artery atherosclerosis regression has been demonstrated in controlled clinical trials. The significance of this regression appears to depend in a complex way on the degree of atherosclerosis present when a regression regimen is initiated. Angiographic trials indicate that lesion change is a continuum, with a gradual transition from progression to stability and regression. Divergent lesion change can be seen in the same patient with a progression of some lesions and a regression of others. This makes it necessary to perform a comprehensive survey of all visible coronary segments when evaluating angiograms to determine the outcome of a clinical trial. An important finding in clinical trials is that new lesion formation can be reduced. This indicates that effective control of atherosclerosis may be possible with procedures now available, but noninvasive coronary artery imaging methods need to be refined.