A clinical trial was done by the Group, Japan to evaluate the efficacy of 26,27-F6-1,25(OH)2D3 on the calcium and bone metabolism of 43 uremic patients on hemodialysis, 24 men and 19 women with a mean age of 50.9 +/- 2.1 years. The initial dose administered orally was 0.05 micrograms/day for 2 weeks. Then the dose was increased every 2 weeks by 0.05 micrograms each time until the dose of 0.3 micrograms/day was reached or until serum calcium increased. 26,27-F6(OH)2D3 increased serum calcium levels significantly at a mean dose of 0.08 +/- 0.03 micrograms/day and at 0.05 micrograms/day of dose comparison in hemodialyzed patients. It decreased the serum level of PTH significantly at a mean dose of 0.14 +/- 0.06 micrograms/day and at 0.3 micrograms/day by dose comparison. The serum level of bone Gla protein increased significantly at a mean dose of 0.18 +/- 0.07 micrograms/day and at 0.25 micrograms/day by dose comparison in the same patients. These results suggest that 26,27-F6-1,25(OH)2D3 has a higher potency in calcium mobilization than 1,25(OH)2D3 in uremic patients on hemodialysis.