In this study of the personality development of four-year-old children, we first attempted to evaluate the personalities of the children attending our research preschool in order to, on the basis of our clinical evaluations, discover a number of factors which would permit us to group the children. We then studied their families to see if we cound find specific and perhaps unique correlations between the children's personalities and the familial milieu. Our preschool nursery operated in four converted apartments of a public housing development on the near West side of Chicago, an area that had been exclusively black for many years. After watching the children in a classroom and observing them in free play, we decided to group the children into three categories on the basis of our clinical assessment of each child's competence, i.e., highly, moderately, or low competent. Our clinical background suggested that play interviews are most effective in assessing four-year-old children. On the basis of a semi-structured play interview, we were able to divide the children into three competence groupings. We examined the factors within the play interviews which contributed to our competence judgments and found it useful to consider three particular aspects of the child's play: organization, interpersonal skills, and content themes. (Author/JM)