Electronegative L5 low-density lipoprotein (LDL) level may be a useful biomarker for predicting cardiovascular disease. We determined the range of plasma L5 levels in healthy adults (n = 35) and examined the power of L5 levels to differentiate patients with coronary artery disease (CAD; n = 40) or patients with hyperlipidemia (HLP) without evidence of CAD (n = 35) from healthy adults. The percent L5 in total LDL (L5%) was quantified by using fast-protein liquid chromatography with an anion-exchange column. Receiver operating characteristic curve analysis was performed to determine cut-off values for L5 levels. The mean L5% and plasma concentration of L5 (ie, [L5]) were significantly higher in patients with HLP or CAD than in healthy adults (P < 0.001). The ranges of L5% and [L5] in healthy adults were determined to be <1.6% and <1.7 mg/dL, respectively. In individuals with L5% >1.6%, the odds ratio was 9.636 for HLP or CAD. In individuals with [L5] >1.7 mg/dL, the odds ratio was 17.684 for HLP or CAD. The power of L5% or [L5] to differentiate patients with HLP or CAD from healthy adults was superior to that of the LDL/high-density lipoprotein ratio. The ranges of L5% and [L5] in healthy adults determined here may be clinically useful in preventing and treating cardiovascular disease.