This report describes trends in treatment admissions for methamphetamine/amphetamine (MA) abuse from 1992 to 2002 in California and assesses predictors of treatment retention and completion. Results show such admissions increasing fivefold and representing a growing proportion of overall treatment admissions. Patients admitted for MA abuse were increasingly diverse in race/ethnicity, older in age, and more frequently under legal supervision status over time. There was a decrease in injection drug use. Several user characteristics played consistent roles as risk factors for noncompletion and shorter treatment retention for both residential and outpatient admissions: having lower than a high school education, being younger at treatment admission, having a disability, having greater severity of MA use, and using injection drugs. Consistently, those with legal supervision status at admission had higher completion rates and longer retention than those reporting no legal status. Overall, findings suggested that clients with greater socioeconomic disadvantage and more severe problems may require greater efforts (e.g., services) to be retained in treatment.