The purpose of this replication study is to establish external validity of the ADSI-S. A convenience sample (n = 114) tested the validity of the ADSI-S with a population aged 18-20 years. Consistency reliability analysis was conducted, correlations were run to determine known-instrument con- struct validity and a logistic regression examined the predictive validity. A Chronbach Alpha of 0.719 was demonstrated. Known instrument construct validity showed a correlation of 0.616. ADSI-S correctly predicted substance use 85.1% of the time. Discussion: The hypotheses forming the rationale for this study were upheld, suggesting external validity.