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Analyses were performed to construct and confirm the validity of new conjoint intake and 6-month follow-up scales for the Addiction Severity Index (A. T. McLellan, L. Luborsky, G. E. Woody, & C. P. O'Brien, 1980) applied to a diverse sample of substance dependence patients (N = 1,008). A multistage scaling strategy identified 5 psychometrically integral addiction problem scales. Exploratory item and factor analyses, confirmatory oblique item clustering, and variance partitioning verified that the scales comprised relatively little common variance and that each retained a substantial amount of unique and reliable variance. Resulting scales (Psychiatric, Drug, Alcohol, Family, and Legal Problems, respectively) were highly internally consistent and structurally stable overall, at intake and follow-up and across gender, age, ethnicity, and substance abuse categories. Concurrent and predictive validity over 2 years were supported for clinical subsamples based on comorbid psychopathology and mood, HIV risk behaviors, personality indices, urine toxicology, and criminal records.