Several scales have been developed to measure self-efficacy for addictive behaviors but there is no such scale applicable to multiple drug users. The Drug Avoidance Self-Efficacy Scale (DASES) was developed to fill this gap. The properties of the scale were evaluated using a sample of 373 young multiple-drug users 16 to 30 years old presenting for treatment at the Addiction Research Foundation. The 16-item scale appeared to be unidimensional. Cronbach's alpha was .9140. Construct validity, evaluated on a subset of the sample, was evident in significant correlations with concurrent measures of drug use severity and differential rates of changes in self-efficacy associated with two types of treatment. The DASES appears to be a reliable and valid scale for the measurement of self-efficacy in multiple-drug users.