Recent cross-sectional studies have indicated that inhalant use might be a vulnerability marker for the development of heroin use. This study is the first prospective investigation of the hypothesized association between early inhalant use and later heroin use. Analyses were conducted using longitudinal data from a community sample of Woodlawn (an all African American community on the South side of Chicago). Six-hundred subjects participated in both the adolescent and the adult assessments (approximately ages 16 and 32, respectively). Youths with a history of inhalant use by age 16 were over nine times more likely to begin heroin use by age 32, even when other plausible risk factors for the development of heroin use were held constant (RR = 9.3; 95% C.I. = 1.3 - 51.3). These findings add to and are consistent with prior cross-sectional evidence from data based on treatment samples and national survey data. The results from this longitudinal assessment support the idea that youthful inhalant use should be regarded as a vulnerability marker for the development of more serious drug use involvement in the form of heroin use.