We studied the relationship between Chlamydia pneumoniae antibodies, C-reactive protein (CRP) and interleukine 8 (IL-8) in 87 patients with ischemic heart disease: 29 patients with acute myocardial infarction, 18 patients with unstable angina pectoris and 40 patients with stable effort angina. We determined in all patients IgG and IgA antibodies to Chlamydia pneumoniae, CRP and IL-8. Species specific antibodies to Chlamydia pneumoniae (IgG and IgA) were detected by indirect ELISA technique (Savyon Diagnostics Ltd, Israel). Interleukine-8 measured by a commercially available ELISA kit (CLB, Amsterdam, The Netherlands). CRP was determined by radial immunodiffusion (Mancini). The IgG antibodies were present in 25 patients (29%), the greatest percentage being noted in patients with unstable angina pectoris (50%). The IgA antibodies were present, as a sign of chronic Chlamydia pneumoniae infection, in 56% of the patients with IgG antibodies. CRP was positive in 52% of the 25 patients with positive IgG antibodies, but in only 34% of the 62 patients without IgG antibodies (p < 0.01). IL-8 was positive in 12% of the patients with IgG antibodies, and in 21% of the patients without IgG antibodies but the difference is not significant (p > 0.05). It is concluded that there is a relationship between the presence of the Chlamydia pneumoniae infection and inflammatory reaction in patients with ischemic heart disease, but the neutrophils are not implied in this process.