It is hypothesized that disordered calcium homeostasis in malignant and non-malignant lymphoproliferative disorders may result from the overproduction of active Vitamin D metabolites in immune cells. The ability of the chloroquine derivatives to inhibit extrarenal 1,25-(OH) 2-D production in sarcoidosis, other granuloma-forming states and lymphoma is being assessed. Based upon the patients entered to date, it appears that 1,25-(OH) 2-D levels drop significantly within days of treatment initiation.