A retrospective evaluation was done on 426 radionuclide cardiac studies performed on female patients at the University of Illinois Medical Center [Chicago, Illinois, USA] from Jan. through Sept., 1980. These procedures included pyrophosphate myocardial scans, resting and exercise 201Tl studies, and gated equilibrium studies. The purpose was to document the incidence and possible consequences of breast artifacts in various cardiac procedures. The incidence ranged from 30-50% of the studies performed, and both the incidence and type of artifact encountered varied with the type of procedure performed. Furthermore, 13-35% of patients had artifacts directly overlying the myocardium. The possible consequences including potential misdiagnosis, interference with computer derived quantitative parameters and the technical maneuvers necessary to avoid or alleviate these problems are discussed.