This study examined the medical records of 2595 consecutive admissions over a 3-year period to an inpatient mixed-gender, hospital-based alcohol and drug detoxification unit. Women reported a significantly different pattern of primary drug use, a younger age, a different pattern of referral sources, and higher rates of parenting status and unemployment. In addition, females were administered prescription medication and medical evaluation tests at a significantly higher rate than males. Multiple regression analyses demonstrated that an opiate as a primary drug of choice was a significant risk factor for dropout. Risk factors for re-admission to inpatient detoxification included: alcohol as a primary drug of choice, residential instability, multiple drug use, single marital status, unemployment, an older age (> 37 years), and treatment dropout at Time 1 in the study. For both the final prediction models, gender was not a significant factor. The treatment implications of these findings are discussed.