We studied the removal of aluminum (Al), iron (Fe), copper (Cu), lead (Pb) and zinc (Zn) with continuous ambulatory peritoneal dialysis, before and after desferrioxamine B (DFO) administration (2 g intravenously) in two patients with chronic renal failure and Al-related osteopathy. Both patients had 4 peritoneal dialysis exchanges (2 liters each) per day. Blood concentrations of Al increased 413% (patient A) and 190% (patient B) after DFO. Patient B had a 15% increase in Fe; other metals remained unchanged. Dialysate efflux Al concentrations had peak post-DFO increments of 761% and 840% in patients 1 and 2, respectively. Peak post-DFO increments in Fe dialysate concentration were 342% and 89.5% in the respective patients. Dialysate/plasma (D/P) concentration ratios of Al increased from pre-DFO levels (mean +/- SEM) of 0.370 +/- 0.048 to 0.523 +/- 0.061 after DFO; similarly, Fe D/P ratios increased from 0.259 +/- 0.053 to 0.446 +/- 0.075 with DFO therapy. These results indicate an increase in the ultrafiltrable proportion of Al and Fe in plasma after DFO administration. During 3 days after DFO, patient 1 had a total removal of Al and Fe of 2.9 mg and 4.9 mg, respectively. Metal removal in patient 2 was 7.6 mg of Al and 2.7 mg of Fe. Peritoneal extraction of other trace metals was minor.