Seventy-eight disease-free children were evaluated by PRIST for total serum IgE in order to establish the normal range for this immunoglobulin and assess its utility, in tropical climates, such as Venezuela, as a diagnostic tool for clinical allergy. Seventy-eight normals were selected from a group of 1053 children, aged 7-12 years from fourteen schools in Caracas. Exclusion from the normal pool was based on nationality, and on historical, clinical, and/or laboratory evidence of atopic and/or infectious diseases, particularly with parasites. In addition to a routine CBC and differential, the following studies were performed: a search for stool ova and parasites; in vitro (RAST) and in vivo (skin prick) testing for specific IgE to Dermatophagoides pteronyssinus, Aspergillus fumigatus, and ragweed. Measurement of antibodies against influenza A and B, adenovirus A2 and B, cytomegalovirus, parainfluenza 1 and 3, herpes simplex, respiratory syncytial virus, Coxsackie B1 to B6, Mycoplasma pneumoniae and Rotavirus was also carried out. Normal serum IgE levels for disease-free children in the age group studied ranged from 1.7-255 mu/ml. The highest average level (Y: 74 mu/ml) occurred at the age of 9 years. These values differed significantly from age-matched control groups of known atopic and helminth-infected children. Thus, once common causes for elevated IgE levels are eliminated, determination of total serum IgE can be utilized as a valuable tool in diagnosis of clinical allergy in countries with tropical climates.