['The association between elevated malondialdehyde-modified low-density lipoprotein (MDA-LDL) and plaque instability in patients with coronary artery disease (CAD) is suspected but not established. The aim of the present study was therefore to investigate the association between serum MDA-LDL and plaque characteristics on angioscopy.', 'A total of 37 consecutive patients with CAD and single-vessel disease who underwent pre-interventional angioscopy, were studied. Using angioscopy at the target lesions, the presence of yellow plaque and complex plaque was examined. Moreover, we evaluated the yellow intensity, which has been shown to have an inverse correlation with the fibrous-cap thickness of the plaques, with quantitative colorimetry to identify a thin-cap atheroma. Serum MDA-LDL in patients with thin-cap atheroma diagnosed on quantitative colorimetry was significantly higher than in patients without thin-cap atheroma (P<0.0009). Univariate logistic regression indicated that serum MDA-LDL was a predictor for thin-cap atheroma (odds ratio [OR], 1.48; 95% confidence interval [CI]: 1.10-1.97; P=0.003) and for complex plaque (OR, 1.22; 95% CI: 1.00-1.48; P=0.046). On multivariate logistic regression serum MDA-LDL was the only independent predictor for thin-cap atheroma (OR, 1.48; 95% CI: 1.10-1.97; P=0.011).'] Is malondialdehyde-modified low-density lipoprotein a useful marker to identify patients with vulnerable plaque?