This proposal represents the continuation of a series of epidemiologic studies on the natural history of behavior problems in preschool children living as permanent residents on Martha's Vineyard Island, seven miles off the coast of Massachusetts. Two studies are proposed. The first is an etiologically oriented investigation into the determinants of behavior problems in three year old children. Stressful life events in parents and in the children themselves, and temperamental characteristics of children are the two principal groups of variables hypothesized to determine the presence of behavior problems. An interview method developed by Brown is used to measure the impact of life events, and parent questionnaires designed by Carey are used to examine the temperaments of children. The dependent variable, behavior problems, is determined from a parent interview, the Behavior Screening Questionnaire of Richman and Graham, and from direct observation of the children in a play paradigm. The sample for this study is the total population of children, aged 0-3 years, arranged in sequential age cohorts. Parents are interviewed once a year up to and including the child's third birthday to collect data on the independent variables. Parents and the children are separately interviewed near the child's third birthday to determine the behavior adjustment of the children. The second study is a 4 year follow-up of children seen as part of the preliminary, prevalence study in 1978. One hundred families will be recontacted to conduct parent and child interviews. In addition, school reports will be obtained. The methods for this study are adopted from the Isle of Wight project reported by Rutter, et. al.. Data from this work will be linked with data from the prevalence study to determine the incidence and duration of behavior problems in young children, and the predictive validity of the behavior assessment methods used in that study. The significance of these studies relates to the primary and secondary prevention of psychiatric disorder in children.