Automated patient education and counseling over the telephone is a convenient and inexpensive method for modifying health-related behaviors. A computer-controlled, telecommunications technology called Telephone-Linked Care (TLC) was used to develop a behavioral intervention to assist smokers to quit and to prevent relapse. The education and counseling is offered through a series of interactive telephone conversations which can take place in the smoker's home. The system's automated dialogues are driven by an expert system that controls the logic. The content is derived from the Transtheoretical Model of behavioral change, principles of Social Cognitive Theory, strategies of patient-centered counseling and recommendations of clinical experts in smoking cessation. The system asks questions, provides information, gives positive reinforcement and feedback, and makes suggestions for behavioral change. Information that the patient communicates is stored and is used to influence the content of subsequent conversations.