Predisposing factors in bladder calculi. Review of 100 cases. One hundred patients, aged twenty to ninety-two years, underwent 111 procedures for removal of bladder calculi. Most patients (88) had some type of bladder outlet obstruction. Two types of stones were identified: those that had apparently formed in the upper tract and been trapped in the bladder (17 cases) and those that appeared to have formed in the bladder in the presence of various types of outlet obstruction. Stone analysis revealed uric acid stones in 50 percent, calcium oxalate stones in 19 percent, and stones of mixed composition in 31 percent. Five patients had metabolic abnormalities predisposing to stone formation; in 2 cases, these abnormalities were discovered during the evaluation for stone disease. Treatment depended on stone characteristics, associated pathology, and the general health of the patient. A review of the literature with regard to the morbidity and mortality of combining treatment of vesical calculi and bladder outlet obstruction secondary to prostatic obstruction is included. 