Accumulating evidence indicates the involvement of heat shock proteins (hsp), a family of stress-inducible proteins, in atherosclerosis. For carotid atherosclerosis an association with an increase in hsp65 antibodies has been demonstrated. To investigate whether such antibodies are also associated with coronary heart disease (CHD) and acute myocardial infarction (MI), an age- and sex-matched study with patients suffering from CHD (n = 114) and MI (n = 89) and healthy controls (n = 76) was performed. All study participants (n = 279) were consecutively recruited according to typical diagnostic criteria. Determination of antibody titres to hsp65 was performed by an enzyme-linked immunosorbent assay (ELISA). Hsp65 antibody titres in CHD showed a significant increase compared to the healthy control group (P = 0.029), however, hsp65 antibody titres were found to be significantly lower in acute MI, compared to CHD (P = 0.005). Alteration in hsp65 antibody titres showed no correlation to established cardiovascular risk factors, e.g. serum total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, blood pressure, smoking, alcohol intake and body weight. In conclusion, serum concentrations of hsp65 antibodies were elevated independently in coronary heart diseases and declined in patients with acute myocardial infarction, indicating a possible involvement of the antibodies in the pathogenesis of this disease.