 The clinical consequences of these abnormalities on bone are not yet known. This trial will study 60 patients with CML in chronic phase, early accelerated phase as detected by cytogenetics only or GIST who are already taking imatinib. Parameters relating to bone metabolism will be checked every 3 months for 2 years. We will determine the incidence of bone abnormalities in this treated population, determine whether fasting serum phosphate can predict for changes in bone metabolism, determine whether there is change in bone density by measuring serial bone densitometry, determine whether oral phosphate replacement can restore phosphate balance, and determine whether there is a dose effect of imatinib on parameters of bone metabolism. 