We are trying to find out the best way for doctors to talk with their adolescent patients about alcohol and drug use. Adolescents 12-18 who are coming to their doctor's office for a routine well-care or follow-up visit will be invited to participate in the study. Participants do not have to have ever used alcohol or drugs. All participants will answer a computerized questionnaire about alcohol and drug use three times. The first one will be at the time of a doctor's visit. The second time will be three months later and the third time a year later. Adolescents who agree to be in the study during the first year will be in the 'control' group. Their doctor will talk to them about drugs and alcohol the same as he/she usually does for all his/her patients. Those who agree to be in the study during the second year will be in the 'intervention' group. Everyone in the 'intervention' group will receive some advice on the computer about their alcohol and drug use. Their doctor will also give them some specific advice about drug and alcohol use. The researchers have chosen what that advice will be, and all doctors involved in the study will give advice according to the study protocol. Participants and their parents will also be given educational information about alcohol and drugs. We will test the effectiveness of the intervention by comparing drug and alcohol use between those who are in the 'control' group, and those who are in the 'intervention' group.