This study examined the associations between lifetime mental disorder, comorbidity, and self-reported postrunaway arrests among 428 (187 males, 241 females) homeless and runaway youth. The analysis examined the pattern of arrests across five lifetime mental disorders (alcohol abuse, drug abuse, conduct disorder, major depressive episode, and posttraumatic stress disorder). The adolescents, ranging from 16 to 19 years old, were interviewed directly on the streets and in shelters in four Midwestern states using computer-assisted personal interviewing. Extensive self-reports of early life history, behaviors since running away from home, and diagnostic interviewing (UM-CIDI and DISC-R) were used to estimate possible disorders. There was a high level of postrunaway arrests reported by the youth; more than half were arrested at least once after the initial runaway, with the average of 4.4 times. Consistent with the hypotheses, there were differential associations between individual mental disorders and involvement with the criminal justice system. Only externalizing disorders such as substance abuse and conduct disorder were related to arrest. Street youth with multiple externalizing and internalizing disorders were more likely to be arrested than nondisordered youths.