Oxidation of low-density lipoprotein (LDL) is considered to be the initial step in the atherosclerotic process. Autoantibodies to oxidized LDL (ox-LDL) have been detected in human serum. We used an enzyme-linked immunosorbent assay technique to measure autoantibody titers in 63 normal subjects and patients with coronary artery disease. Thirty-five patients underwent coronary angiography for suspected coronary artery disease. Patients were divided into the following categories: group 1, 20 healthy young volunteers; group 2, 8 patients age-matched to the catheterization patients; group 3, 10 patients with normal coronary angiograms; and group 4, 25 patients with angiographic coronary artery disease. Autoantibody titers to ox-LDL were group 1, 0.142 ± 0.023; group 2, 0.197 ± 0.039; group 3, 0.183 ± 0.038; and group 4, 0.340 ± 0.026. There was no statistical difference among groups 1, 2, and 3, but the difference between these groups and group 4 was highly significant (p < 0.05). This study demonstrates that (1) autoantibodies to ox-LDL can be detected in normal subjects and in patients with abnormal coronary angiograms and (2) significantly higher titers of autoantibodies to ox-LDL were seen in patients with angiographic evidence of coronary artery disease.