Schistosomiasis is a trematodal infestation that affects over 200,000,000 people in Africa, Asia, and South America. To this number must be added the many potential victims of this disease who become exposed to it during military, political, and humanitarian visits to these areas, causing consequent difficulty in diagnosis and treatment when they return to their native countries where the disease is not indigenous. During the four to six week period of trematodal migration, systemic disturbances often referred to as the Katayama syndrome are common. Hematologic examination at this time will disclose a normochromic or hypochromic anemia associated with an eosinophilia of 10 to 60 per cent. At this stage a cercarial skin test may be positive, permitting early commencement of a curative course of systemic antimony therapy. Subsequently, however, with deposition of ova in the appropriate viscera and organs, irreversible effects of visceral schistosomiasis lead to complications which must be treated by surgery. The urinary tract is peculiarly susceptible to ovideposition by S. hematobium and the vesical irritant sets up a local inflammatory reaction which provides cystoscopic evidence of disorder. With progression of the bilharzial cystitis the vesical epithelium develops granulomatous masses. There may be varying degrees of stenosis in the ureter or fibrotic distraction of the orifice associated with ureterovesical reflux. Hydroureter may become massive with consequent disturbance in renal function. Surgical treatment is aimed at providing the greatest degree of relief from the irreversible effects of urinary schistosomiasis. This includes cystoscopic meatotomy, ureteral bouginage followed by regular dilatation, and even possible ureteral resection if the stricture is impossible or if repeated dilatations prove ineffectual. Transplantation of the ureters into the pelvic colon is indicated if there is a completely disorganized bladder with internal or external fistulas, while ileocystoplasty may permit an increase in bladder capacity when this is desirable. The alimentary tract is particularly affected by S. mansoni, especially that part of the alimentary system drained by the inferior mesenteric vein.