We conducted a phase II trial of doxercalciferol, a vitamin D2 analogue, in 15 patients with MDS. Each received doxercalciferol 12.5 microg orally daily for 12 weeks. Nine of 15 patients completed the prescribed course and of these, six had stable disease. No patient had a response (IWG criteria) and overall eight patients experienced progressive disease while on therapy. Two patients with chronic myelomonocytic leukemia (CMML) had a marked rise in monocytes on study. Overall the treatment was well tolerated. One patient was removed from study due to hypercalcemia. We conclude that short-term treatment with doxercalciferol has limited activity in patients with MDS.