Variable tissue overloading can alter the removal rate of iron and aluminum from uremics. Owing to its higher affinity to deferoxamine (DFO) and higher plasma concentrations, Fe could impair Al removal in cases of simultaneous body burden. Fe and Al plasma kinetics and mass transfer were therefore studied in 12 uremic patients with different Fe and Al status: six with normal ferritin levels (less than 400 micrograms/L [ng/mL]), and Al 1.4 to 4.7 mumol/L (40 to 131 micrograms/L) (group A); six with increased ferritin (greater than 2,000 micrograms/L), and Al 1.7 to 17 mumol/L (47 to 476 micrograms/L) (group B). DFO (40 and 80 mg/kg in a random sequence) was administered once a week during the first hour of the first hemofiltration (HF). The results show that in both groups and with both DFO doses, maximum Fe and Al mass transfer was achieved in the first and second HF, respectively. The 80-mg/kg dose of DFO significantly raised Al mass transfer in both groups, whereas Fe mass transfer was only slightly affected. Even though plasma Fe levels were almost always higher than Al, Al mass transfer eventually exceeded that of Fe, in both Fe-normal and Fe-overload patients. The bias towards Al in mass transfer was enhanced in both groups in the second HF, and at the higher DFO doses. Thus, DFO once a week reduced Fe loss to less than 30 mumol/wk in patients with normal ferritin levels. In both Fe and Al overloaded patients, Al can be removed, and Al mass transfer may often exceed Fe mass transfer, depending on the degree of tissue burden, the time from DFO infusion, and the DFO dose.