The purpose of this Stage I/II intervention study (that is, Stage II for drug use and Stage I for alcohol use and smoking) is to test the efficacy of a brief, computerized motivational intervention for substance abuse among post-partum women. The study will randomly assign 350 post-partum women to either intervention or control conditions, with intervention itself taking approximately 30 minutes in the period before the participant leaves the hospital. Inclusion criteria will include post-partum status, age between 18 and 45, ability to understand spoken English, and meeting criteria for one of the three substance use groups: any illicit drug use in month prior to pregnancy, meeting T-ACE criteria for problem alcohol use, or smoking in past month. Exclusion criteria will include receipt of narcotic pain medication in the past 3 hours, no sleep since giving birth, and inability to provide informed consent (e.g., due to psychosis or other clear cognitive impairment).