Current therapeutic options for myelodysplastic syndromes (MDS) are limited and, aside from bone marrow transplantation, none have proven superior to supportive measures alone. Preclinical investigations have indicated the potential therapeutic role for vitamin D in the treatment of MDS. However, because of the dose-limiting toxicity of hypercalcemia, past clinical trials with vitamin D have been forced to utilize low doses, with promising but inconsistent results.