A recent study of arrest data show that African Americans are 2.5 times more likely to be arrested for marijuana possession offences than Whites, even though general prevalence estimates show that they are no more likely to be using. The current study investigates the purchase patterns of marijuana users from the 2002 National Survey on Drug Use and Health (NSDUH) to evaluate whether differences in purchasing behaviors exist across racial groups. Although in general people who purchase marijuana are more likely to buy in private settings and from someone they know, this analysis shows that African Americans are statistically more likely to engage in risky purchasing behaviors that increase their likelihood of arrest. Using trivariate probit regression with demographic, drug use, and drug market covariates, analyses reveal that African Americans are nearly twice as likely to buy outdoors (0.31 versus 0.14), three times more likely to buy from a stranger (0.30 versus 0.09), and significantly more likely to buy away from their homes (0.61 versus 0.48). These results provide an additional explanation for the differential in arrest rates between African Americans and Whites.