Gallium, a semi-metallic element in group 13 (IIIa) of the periodic table, has shown efficacy in the treatment of several apparently diverse disorders. These disorders can be broadly categorized as:(a) accelerated bone resorption, with or without elevated plasma calcium;(b) autoimmune disease and allograft rejection;(c) certain cancers; and (d) infectious disease. Gallium is effective in suppressing bone resorption and, when present, concomitant elevated plasma calcium. This antiresorptive activity has led to its clinical use in treating hypercalcemia of malignancy (Warrell and Bockman, 1989) and Paget’s disease of bone (Bockman and Bosco, 1994; Bockman et al., 1989, 1995). Gallium has also shown clinical efficacy in suppressing osteolysis and bone pain associated with multiple myeloma and bone metastases (Warrell et al., 1987a, 1993), and has been suggested as a treatment for osteoporosis (Warrell, 1995). Accumulating evidence indicates that, in addition to antiresorptive activity on bone, gallium also has anabolic activity. The semimetal also shows specific immunomodulating activities. It is effective in suppressing adjuvantinduced arthritis (Matkovic et al., 1991), experimental encephalomyelitis (Whitacre et al., 1992), experimental autoimmune uveitis (Lobanoff et al., 1997), and allograft rejection (Orosz et al., 1996) in animal models, without being generally immunosuppressive. Other studies have suggested possible efficacy in mouse models for asthma (Apseloff et al., 1996), type I diabetes (Flynn et al., 1992), and endotoxic shock (attenuation of LPS-induced hepatitis; Krecic et al., 1995). Several in vitro experiments have found gallium effective at inhibiting T cell and macrophage activation and in suppressing the secretion of certain cytokines by these cells (Whitacre et al., 1992;