The simultaneous use of deferioxamine (DFO) and deferiprone (DFP) has an additive effect in iron excretion in transfusion-dependent thalassemic patients. In a prospective study, we evaluated the safety and effectiveness of combined therapy with these two chelators. Fifty patients with beta-thalassemia were uniformly treated with DFP for 4 days per week and combined therapy with DFP and DFO for 3 days of the week. Efficacy was evaluated by ferritin and cardiac shortening fraction (SF). Hepatic hemosiderosis was also assessed by estimation of the T2 relaxation time by magnetic resonance in a subgroup of patients. Forty-three patients completed 1 year of therapy. Mean ferritin decreased from 3363.7 +/- 2144.5 microg/L to 2323.2 +/- 1740.8 microg/L (P < 0.0001). The reduction was significant even in the group of patients with ferritin <2500 microg/L. Significant improvement in T2 relaxation and SF was observed. The most common adverse events were gastrointestinal symptoms (20%) and transaminasemia (18%). The rate of agranulocytosis was 4.2 cases per 100 patient-years. Prolonged use of combined therapy with DFP and DFO is effective in decreasing iron load and improving cardiac function. Its possible association with higher incidence of agranulocytosis emphasizes the need for close monitoring.