Thorotrast (a colloidal suspension of thorium dioxide) was introduced to the radiological armamentarium in 19281and rapidly achieved widespread popularity as a contrast medium for cerebral angiography, hepatolienography, myelography, and salpingography. Since that time the accumulation of cases of malignant disease, fibroses of vital structures, and anemias which might be attributed to thorium dioxide has virtually prohibited its use, although doubts have been raised concerning the mechanism of their causation. This literature has been recently reviewed by Looney.2 Although the majority of carcinomas that occur after administration of thorium dioxide suspension are found in the liver,2local tumor induction has also been reported in man3and animals.4This induction is well illustrated by the following case. A 48-year-old Portuguese woman underwent salpingography as part of a sterility investigation in 1938. Presumably a colloidal suspension of thorium dioxide was the radiopaque agent employed. Apparently at least