Objective. —To estimate the prevalence of elevated lead levels among children in Orange County, California, and to evaluate the appropriateness of a universal pediatric blood lead screening policy in this community. Design. —Venous blood lead testing was conducted and results were analyzed according to seven blood lead strata ranging from less than 0.50 μmol/L (10 μg/ dL) to 3.35 μmol/L (70 μg/dL) or higher. A cost analysis of the lead-testing program in Orange County was conducted. Setting. —Children meeting poverty eligibility criteria and attending the Child Health and Disability Prevention Program, the state's implementation of the federal Early and Periodic Screening, Diagnosis and Treatment (EPSDT) services program. Participants. —A total of 5115 Orange County children between 12 and 72 months of age using EPSDT services from March through December 1992. Main Outcome Measures. —Blood lead levels and associated costs of the testing program stratified by level of blood lead elevation. Results. —Blood lead levels of 0.50 μmol/L (10 μg/dL or higher were found in 371 children (7.25%; 95% confidence interval, 6.66% to 7.85%), but only six children (0.12%; 95% confidence interval, 0.04% to 0.20%) had elevations greater than 1.20 μmol/L (25 μg/dL). Five children (83.3%) had histories of lead consumption unrelated to ingestion of lead-containing paint but related to the use of lead-containing folk remedies and cooking utensils. Costs for detection of children with blood levels elevated to 0.50 μmol/L (10 μg/dL) or higher was $310 per child and for levels of 1.20 μmol/L (25 μg/dL) or higher was $19139 per child. Conclusions. —These data suggest that lead poisoning is not a major public health problem among Orange County children and detection of infrequent cases would involve a high cost per child. In jurisdictions with newer housing, initial screening for a history of possible lead exposure alone may offer reasonable efficacy that is cost-effective. The scope of lead-testing programs should be determined according to local needs and conditions. (JAMA. 1993;270:69-71)