We reviewed 71 United States-based MacAndrew Alcoholism Scale (MAC), as revised (MAC-R) studies totaling almost 32,000 Ss, with adolescent and adult substance abusers, from studies published since the last MAC reviews (1989) through 2001. Results suggest that the MAC, and to some extent, the MAC-R, significantly correlates with measures of alcohol and substance abuse in both male and female adolescents and adults, across a diverse spectrum of the use-abuse continuum. Nonclinical groups (100%) scored below the clinical ranges on the MAC/MAC-R, while 79% of adolescent substance abusing groups scored > R 23, indicative of problems with substance abuse. Persons who abused alcohol, drugs, and polydrugs had mean MAC/MAC-R scores > 23, which ranged from 77% to 100% of the cases. The MAC/MAC-R does well in discriminating persons who abuse substances compared to nonclinical, nonabusing groups, but appears to lose diagnostic efficiency with psychiatric patients, and especially with medical patients with seizure disorders. Using R > 25 seems to improve diagnostic accuracy with this population. Meaning of false positives and false negatives were explored and discussed.