The SDSS is a semi-structured, clinician-administered interview that assesses DSM-IV dependence and abuse and ICD-10 harmful use for alcohol and other drugs for the previous 30 days. It assesses frequency and severity of symptoms. The SDSS consists of 7-10 screening questions for alcohol and each drug category and 13 symptom items. The SDSS is useful in clinical settings because it has been designed to provide an indication of recent severity of substance abuse and dependence on alcohol, specifically by drug type. It also offers unique advantages as a measure of treatment outcome that may be more sensitive to changes in clinical status than outcome measures routinely used, such as self-report substance use, urinalysis results, or diagnostic status. In research settings, the SDSS can be used as a baseline and follow-up measure in alcoholism and drug abuse treatment studies and other studies requiring quantification of severity keyed specifically to DSM-IV or ICD-10 criteria. The SDSS is available in pencil-and-paper and interview formats and can be administered by a clinician in 30-45 minutes. In a study comparing 5 diagnostic instruments (SCID, CIDI-2, DIS-IV, DSM-IV Checklist, SDSS) for suitability for use in the CTN Clinical Trials Network, the SDSS was ranked 5th (Forman et al 2004). An 11-item "Lite" version of this scale has also been used in CTN research.