The case of Fred M. is taken from a longitudinal study of individuals from birth through twenty-one years and beyond. Each child was seen by appointment, near his birthday, once a month during infancy, then every three months until three years, and every six months through eighteen years. The observations included tests of mental and motor ability, anthropometric measurements, tests of development of reflexes and vegetative function, physical examinations, body photographs, X-rays of hand and knee, a series of personality and interest questionnaires, and ratings and notes on the child and his parents, as seen in the testing situation. In addition there were several interviews with the parents in the home, concerning family adjustments and attitudes. On the basis of home visits ratings were made of socio-economic status and other relevant aspects of the home and family.