Abstract Red cell carbonic anhydrase B and C isozymes and hemoglobin F were studied by the single radial immunodiffusion technique in lead workers exposed to low concentrations of lead. The lead contents, δ-aminolevulinic acid dehydrase and glutathione levels were simultaneously determined. Carbonic anhydrase B, glutathione and δ-aminolevulinic acid dehydrase activity in lead-exposed workers showed relatively low values compared to those of normal subjects not exposed to occupational lead exposure in the past or present. Subjects with blood lead contents of 30 μg per 100 ml or higher showed a significant increase in hemoglobin-F and a significant decrease in carbonic anhydrase B and glutathione levels. These findings indicate that the syntheses of these red cell components are affected by lead, and hence in addition to δ-aminolevulinic acid dehydrase activity, these components were also found to be of clinical value for the diagnosis of subclinical lead poisoning.