In this non-randomized prospective study, liver and spleen iron concentrations were monitored annually over a 4-year period by non-invasive Superconducting Quantum Interference Device biomagnetometry in 54 beta-thalassaemia major patients (age, 7-22 years) receiving treatment with deferiprone (75 mg/kg/d). Median liver iron concentrations increased significantly from 1456 to 2029 and 2449 microg/g(liver) at baseline, after 2.0 and 3.2 years respectively. Another group of 51 thalassaemic patients (aged 4-34 years) who received desferrioxamine s.c. for 1.9 years increased their liver iron concentration from 1076 to 1260 microg/g(liver). Taking into account the increase of the daily iron input from transfusions of 3.6 mg/d, caused by weight gain in 67% of the patients treated with deferiprone, a larger total body iron elimination rate was achieved after 2 years than at baseline. A negative ferritin change was observed in 51% of the patients. In 15 non-splenectomized patients, liver iron significantly increased from 1260 to 1937 microg/g(liver) (P < 0.01), but serum ferritin remained stable at 2100 microg/l, as did the spleen iron concentration at 1200 microg/g(spleen). A two-compartment model may predict an average chelation efficacy for desferrioxamine and deferiprone, with a saturation effect of the latter, for a certain chelation and transfusion regimen by a single liver iron quantification.