The diagnosis and the effects of treatment of anemia were assessed in children aged 6-71 months. A total of 1,161 preschool children from a health center of INAMPS (Instituto Nacional de Assistência Médica e Previdência Social) in Recife, Pernambuco, was studied. Hemoglobin was determined by the method described by Hainline. WHO criteria were used to identify anemia. According to their age, nutritional status and family income, the children were divided into groups, and those with anemia were treated with ferrous sulphate and an anti-helminthic (mebendazole). Anemia prevalence was substantially higher in children aged 2 years, and a statistically significant association (0.01 level) was found between anemia and nutritional status and family income. After treatment, hemoglobin values were normal in 40% of the anemic children; simultaneously, mean hemoglobin values increased from 9.11 to 10.3 g/dl which was statistically significant (p less than 0.001). This investigation is part of a collaborative study performed in four Brazilian states to offer "know-how" to a national program for combating iron deficiency anemia.