To determine the prevalence and correlates of psychiatric disorders among preschool children in a primary care pediatric sample. In a two-stage design, 3,860 preschool children were screened; 510 received fuller evaluations. For quantitative assessment of disorder (> or = 90th percentile), prevalence of behavior problems was 8.3%. "Probable" occurrence of an Axis I DSM-III-R disorder was 21.4% (9.1%, severe). Logistic regression analyses indicated significant demographic correlates for quantitative outcomes (older age, minority status, male sex, low socio-economic status, father absence, small family size) but not for DSM-III-R diagnoses. Maternal and family characteristics were generally not significant. Child correlates included activity level, timidity, persistence, and IQ. Overall prevalence of disorder was consistent with rates for older children; correlates varied by approach used for classification.