The dose-response relationship between erythrocyte protoporphyrin (EP) and blood lead (PbB) was investigated among children with different subgroups of iron status. The data bank from Santo Amaro City, Brazil, was taken to study 490 children aged 1-9 years who lived at less than 900 m from a primary lead smelter. Mean PbB was 58.9 +/- 25.3 micrograms/dl and mean EP was 87.1 +/- 68.1 micrograms/dl. At PbB levels lower than 60 micrograms/dl, the dose-response curve for EP versus PbB followed the classical pattern; children with low iron status showing greater EP "response" than those with typical iron status and those with high iron status, after controlling for the effects of age and racial group. Among children with PbB > or = 60 micrograms/dl, EP response increased according to the following order: typical < low < high iron status.