Results indicated that among females, early-onset MAMP use was significantly associated with depressive disorder, conduct disorder, and amphetamine use disorder. Among males, early-onset MAMP use was significantly associated only with amphetamine use disorder. Among both genders, lifetime prevalence of amphetamine use disorder was significantly higher for adolescent MAMP users who began using the drug before the age of 16 years. Participants were 299 adolescents with MAMP use who were recruited from 2 juvenile detention centers in Taiwan from September 1998 through March 2002. Participants were administered the Kiddie epidemiological version of the Schedule for Affective Disorders and Schizophrenia (K-SADS-E) to screen for substance use disorder and other psychiatric comorbidities. Follow-up studies should utilize longitudinal methods to examine the course of MAMP use from first use to formation of psychiatric morbidity. Tables, references