The therapeutic use of radioactive colloidal gold Gold Au-198 (Au198) was first described by Sheppard et al., who reported on intravenous use in 1947. Its possibilities for the treatment of various malignant processes have been explored in great variation. Gold Au-198 is an antineoplastic, diagnostic aid (liver imaging) and radioactive agent. Thus, intracavitary instillation of colloidal radioactive gold Au-198 was used for treatment of patients with multiple papillomata of the bladder. Approximately 300 mc. of gold was instilled into the bladder for four to six hours to deliver a dose of about 4,000 to 5,000 r to the bladder epithelium. The treatment had no harmful side-effects locally or on the general condition of the patient. It was also used to estimate the hepatic blood flow in children with active or progressive chronic hepatitis. Gold Au-198 was used in the combination therapy of rectal cancer.