Although a variety of cardiac abnormalities have been described in AIDS patients, it is unclear whether these are incidental findings or they presage clinically important heart disease. Also, because AIDS-related complex (ARC) is, in general, a milder form of AIDS, we wondered if echocardiographic abnormalities would differ in kind or in frequency, when compared with AIDS. To answer these questions, we studied the echocardiographic findings and the demographic features of 15 patients with AIDS and 24 patients with ARC. The ARC group had abnormalities in the same proportion as in our AIDS group, except for echocardiographic mitral valve prolapse. The MVP, however, did not appear to be due to intrinsic valvular disease. Rather, echocardiographic MVP was associated with low body weight (P = .02) but not with the cardiac signs or symptoms of MVP. Four AIDS patients had LV dysfunction. Of the echocardiographic variables, only a wide EPSS was significantly correlated with survival, as it is in other populations. We conclude that although echocardiographic abnormalities are common in AIDS and ARC patients, most of these abnormalities lack clinical significance.