The authors studied 134 patients with unstable angina pectoris symptoms and 32 subjects without coronary artery disease (CAD) for the presence of classical risk factors such as hypercholesterolemia, smoking, and family history of CAD. In addition they analyzed plasma insulin levels, lipoprotein (a) (Lp [a]) levels, and antibody titers against Chlamydia pneumoniae. All patients had a heart catheterization. Patients with diabetes mellitus were excluded from the study. Fasting insulin, low-density lipoprotein (LDL) cholesterol and Chlamydia pneumoniae immunoglobulin G (IgG) and IgA antibody titers did not show any difference in CAD from healthy control subjects, whereas Lp(a) was increased and high-density lipoprotein (HDL) decreased in CAD patients. These data indicate that lipoprotein (a), low HDL cholesterol, and smoking, but neither hyperinsulinemia nor elevated Chlamydia pneumoniae titers, are risk factors or predictors for CAD.