Substance use disorder diagnoses were used as a treatment outcome measure in a randomized comparison of day treatment (DT) and day treatment plus contingency management (DT+) among homeless persons with primarily crack/cocaine disorders. Participants (N = 127, DT+ = 69, DT = 58, 73.2% male, 82.7% African American) were assessed at baseline and 6-month treatment completion. Binary positive and negative diagnostic outcomes for cocaine, marijuana, and alcohol were compared by treatment group. DT+ was 2.1 times more likely to have a positive treatment outcome than DT. Concordance between diagnostic change and point and continuous abstinence outcomes were found. The use of diagnostic change can be a practical addition to drug toxicology and self-report treatment outcome measures for research and practice.