r NHE World Health Organization defines health as a state of complete physical, merltal and social well-being, and not merely the i ,absence of disease or inflrmity. If we accept this deflnition we should study the physical health of young males in terms not only of the presence or absence of pathology such as tuberculosis, but also in terms of their growth, nutrition and physiological adaptability. Their mental health must be studied not only to determine the prevalence of mental defect or neurosis, but also for more positive indications of mental well-being, for example the effectiveness with which the young men use their abilities, their capacity to maintaiIl co-operative human relationships, the degree of their emancipation from the home, their resilience in face of change, and the realism of their outlook. We need to study the social health of young men, not only as shown by absenteeism rates and labour turnover, for instance, or delinquency, or the problem of the unclubbable youth, but we should also inquire into the satisfactions which they find at work and whether they have begun to think of the social responsibilities of mamage, parenthood and citizenship in a democratic society. As we are concerned in this study with eighteer-yearolds who are in a phase of transition and active development, these more positive aspects of health are related to physical, intellectual and emotional maturation. In this investigation we have studied some aspects of the physical, mental and social health of young men. We were interested in the following questions: What is the health of these youths ? What stage have they reached in their growth, physical, mental and social ? How do environmental forces such as family background, educational and vocational opportunities, and social class combine to influence the young men ?