This is a prospective study of the effects of prenatal marijuana exposure on child behavior problems at age 10. The sample consisted of low-income women attending a prenatal clinic. Half of the women were African-American and half were Caucasian. The majority of the women decreased their use of marijuana during pregnancy. The assessments of child behavior problems included the Child Behavior Checklist (CBCL), Teacher's Report Form (TRF), and the Swanson, Noland, and Pelham (SNAP) checklist. Multiple and logistic regressions were employed to analyze the relations between marijuana use and behavior problems of the children, while controlling for the effects of other extraneous variables. Prenatal marijuana use was significantly related to increased hyperactivity, impulsivity, and inattention symptoms as measured by the SNAP, increased delinquency as measured by the CBCL, and increased delinquency and externalizing problems as measured by the TRF. The pathway between prenatal marijuana exposure and delinquency was mediated by the effects of marijuana exposure on inattention symptoms. These findings indicate that prenatal marijuana exposure has an effect on child behavior problems at age 10.