Plasma levels of IL-3 and IL-7 were studied in 23 patients with homozygous beta-thalassemia in order to determine whether these cytokines are involved in abnormalities in erythropoiesis and immune responses as observed in thalassemic patients. No significant difference was found in plasma IL-7 concentrations between thalassemic patients and healthy controls and it was suggested that IL-7 is not a cytokine involved in cellular immunological alterations in beta-thalassemia. However, the number of thalassemic patients with detectable IL-3 concentrations was significantly higher. It was concluded that IL-3 production has to be studied in detail in order to learn more about the involvement of this cytokine in erythropoiesis of thalassemic patients.