The purpose of this study is to if a brief motivational intervention, compared to health education sessions, reduces alcohol and marijuana use and is related to fewer sexually transmitted infections (STI)in emerging adults who are engaging in alcohol and marijuana use.

Inclusion Criteria:

• Be between the ages of 18 and 25
• Binge drink (5 or more drinks in a 2-hour period for men, 4 or more for women) at least monthly
• Use marijuana at least weekly
• Have been heterosexually active in the past six months
• Are not married
• Have not been living with a sexual or romantic partner for more than 6 months
• Be English speaking
• Reside within 20 miles of Providence, RI and plans to stay in the geographic area for the next 15 months
• Provide contact information for at least two verifiable locator persons

Exclusion Criteria:

• Have DSM-IV diagnosis of drug abuse or dependence (other than nicotine, marijuana)
• Have DSM-IV diagnosis of alcohol dependence