The suitability of fitting a two-parameter logistic item response model to the Drug Use Screening Inventory (DUSI) was assessed. In a sample of 846 adolescents, each of the 10 domains was found to be unidimensional. Invariance of the item parameters across different groups was also observed. The reliability coefficient, based on item response theory, was found to be superior. The results of these analyses indicate that the DUSI has sound psychometric properties.