The present study examined whether measurement of hemoglobin-acetaldehyde (HbA1-AcH) using an improved methodology may be useful as a biological marker of alcohol abuse. Red blood cell hemolysates of 182 patients consecutively admitted to the drug and alcohol treatment unit of our institution were analyzed for HbA1-AcH concentration using cation exchange HPLC. Mean HbA1-AcH of those who claimed to drink >6 drinks/day [mean = 0.055 (% total hemoglobin), SD = 0.051] was significantly higher than the mean of those who drank <6 drinks/day (mean = 0.026, SD = 0.0174). The greatest sum of sensitivity (67%) and specificity (77%) came with a cut-score of 0.030 area% of total hemoglobin. A cut-score of 0.080 produced a 100% specificity, but lowered the sensitivity to 20%. The Pearson product moment correlation (r) between HbA1-AcH and reported drinks per day was r = 0.30 (p < 0.001). There was no significant difference in the association of HbA1-AcH and reported drinking between males and females, and the small difference observed was shown to be entirely associated with differences in hemoglobin levels between the sexes. Cocaine use did not significantly alter the correlation between reported drinking and HbA1-AcH levels. Hemoglobin levels were shown to have a significant correlation with HbA1-AcH independent of drinking. HbA1-AcH was shown to have a better sensitivity and specificity than gamma-glutamyltransferase, ALT, AST, or mean corpuscular volume in this population. The results suggest that HbA1-AcH may be a useful marker to help detect alcohol abuse, especially in populations where other markers have been shown to fail.