Designed to establish a causal relationship between childhood victimization and young adults' substance abuse, this study also examined depression's role as mediator in that causal relationship. The study employs child-abuse measures that weigh both the type (sexual, physical) and the persistence of abuse. The study took as its substance-abuse measures the DSM-IV criteria for current alcohol abuse, current marijuana abuse, and current drug abuse. Data from the first 5 waves of the National Youth Survey (NYS) was employed, along with data from its 7th wave, to establish the temporal order needed to determine causal relationship. Childhood physical abuse proved a strong predictor of young adults' current substance abuse, although sexual abuse did not. Depression was shown to mediate the relationship of physical abuse to current alcohol abuse and current drug abuse, but not to current marijuana abuse.