PIP: Adolescents often feel like sexual beings because of the physical and psychological changes produced by their hormones. Adolescents are sometimes disturbed by their newly occurring sexual fantasies and by lack of understanding from their parents of the changes they are experiencing. These factors together with social pressures of various kinds occasionally make the adolescent forget that decisions about how to behave sexually should be made by the individual, not by others. Adolescents should be able to evaluate personal relationships for their positive or destructive qualities. Decisions by adolescents about their sexual behavior and about when a personal relationship should become a sexual relationship are made more difficult by the conflicting social, group, and interpersonal pressures they face. In a good sexual relationship as in a good friendship, the 2 persons feel confident and behave honestly with each other. Neither dominates the other, and the relationship is pleasurable rather than negative for both. According to research, the 1st sexual relations of an adolescent often occur with an adult. Sex is usually unpremeditated and unplanned. Many adolescents are disappointed in their 1st sexual experiences, which may have occurred in unfavorable circumstances. The combination of inadequate sex education and knowledge of what to expect and unrealistically high expectations from movies or stories probably are principal causes of disappointment. Adolescents in the process of maturing from childhood into adulthood are not completely prepared psychologically or socioculturally for parenthood. In Mexico, 75% of 1st unions are believed to begin before the woman is 20 years old. Most adolescents who become pregnant do not use contraception. In 1976, only 16% of new family planning acceptors were believed to be 15-19 years old. The proportion of births to mothers under 18 was estimated to have increased from 3.1% in 1968-70 to 10% in 1976. Adolescent pregnancies, especially those in very young mothers, are at high risk of complications. Adolescent parents may suffer psychological complications and may face problems of incomplete education, restricted employment opportunities, and marital instability.