The concentration of aluminum (Al) in serum, urine, and bone, as well as bone histomorphometry parameters were studied before and 1 year after kidney transplantation (Tx) in 20 dialyzed patients. One year after Tx, serum Al fell significantly from 50.3 +/- 8.8 to 23.9 +/- 2.7 micrograms/l, (53% fall). Bone Al content also decreased significantly from 62.9 +/- 9.0 to 36.5 +/- 7.0 micrograms/kg bone weight, but urine Al excretion was still above normal. The repeat bone histomorphometric examination showed a good recovery of bone resorption which correlated well with serum parathyroid hormone levels, but poorer recovery of indices of bone formation and of the extent of Al deposits in the bone as shown by aluminum staining.