This is a project to study the long-term effects of the treatment of acromegaly with the long-acting somatostatin analog, octreotide. Patients are treated in an unblinded fashion with octreotide as long as it is medically necessary. Treatment and prevention of gallbladder sludge and gallstones, common side effects of long-term octreotide therapy, is being attempted with ursodeoxycholate, a bile salt which has been used to dissolve gallstones in the general population. Patients who are candidates for treatment with octreotide, and who have normal gallbladders as determined by ultrasonography, are randomized to receive either ursodeoxycholate or placebo in order to study whether ursodeoxycholate is effective in preventing octreotide-induced gallbladder sludge or stones are treated in an unblinded fashion with ursodeoxycholate in an attempt to dissolve the sludge or stones. Fifteen patients have been randomized to masked treatment with ursodeoxycholate, and nine patients have been treated unmasked for sludge or stones. To date, pre-existing gallstones have dissolved in 3 of 5 patients and pre- existing sludge has disappeared in 2 of 4 patients during ongoing therapy with octreotide. We are continuing to enroll patients in the randomized prospective trial, as well as to treat with ursodeoxycholate all patients who develop octreotide-induced gallbladder abnormalities.