Adolescents enjoy animated-action computer games that capture and hold attention. In this study, the use of computer-assisted instruction in improving knowledge and attitudes in favor of decreased teenage pregnancy is evaluated. Computer-assisted health education is an interactive process and simulates reality. Teenagers explore alternatives and outcomes, and experience consequences of behavioral choices. Two games were designed to promote understanding of the impact and cost of sexual behaviors and parenthood, as well as provide sexual survival skills. Educational evaluation in high schools showed improvements in knowledge and attitudes in these sensitive areas. Test instruments based on the content of each game were developed to assess the impact of the two interventions. Half of the 718 teenagers used the educational programs, and half served as matched control subjects who did not use computer games. Players rated the games highly and evaluated them positively. Measures of 19 factual and psychologic factors associated with pregnancy and parenting were separately made for control and experimental groups. Teenagers who played the games gained knowledge and positive attitude changes to a significantly greater extent than did the comparison group. "The Baby Game!" users increased their knowledge of costs of birth and of costs in money and time of child rearing. "Romance!" users would seek more professional help, had a better understanding of risk of pregnancy, learned more effective means of contraception, and had greater acceptance of oral contraceptives. Teachers and teenagers found the computer games acceptable and fun, and the games reduced counseling time in physician's offices. Computer-assisted instruction is a useful means of providing health education and a promising intervention for adolescent pregnancy.