In a study of emotional and behavioral problems seen in children attending pediatric primary care clinics in a health maintenance organization, parents of 789 children 7 to 11 years of age completed a behavior screening questionnaire, the Child Behavior Checklist. Of the 195 (24.7%) children identified by the checklist as disturbed, 126 were given a detailed psychiatric assessment using the Diagnostic Interview Schedule for Children, a structured psychiatric interview of known validity and reliability. A randomly selected group of 174 nondisturbed children was also assessed. The pediatricians' judgment about the presence of emotional and behavioral problems, made at the index clinic visit, was compared with diagnoses made from the computer-scored interviews. Pediatricians diagnosed one or more such problems in 5.6% of the children (weighted estimate: 95% confidence limits 3.8% to 7.6%), compared with 11.8% (95% confidence interval 9.3% to 13.5%) based on the interview with the parent. Pediatricians were highly specific, ie, 84% of children assessed as nondisturbed had no psychiatric disorder, but they showed low sensitivity, ie, they only identified 17% of the children with behavioral or emotional problems, giving a "hidden morbidity rate" of 83% (ie, 83% of cases were not identified). The role of primary care pediatricians in the identification, prevention and treatment of what has been called "the new morbidity" is discussed. We suggest that, on the basis of these findings, emotional and behavioral problems in children have to be seen as "the new hidden morbidity."