In view of diseases associated with inhalation of asbestos fibers, interest attaches to the question of whether risks are presented by ingestion of asbestos or mineralogically related fibrous-shaped particles reported in drinking water supplies. Experimental animals (hamsters) were maintained on filtered drinking water with and without addition of mineral particles. A peritoneal mesothelioma, pulmonary carcinoma and two early squamous cell carcinomas of the forestomach were found in hamsters so exposed to a preparation of amosite asbestos. These tumors could not be specifically attributed to amosite, but they show that hamsters of the strain used were capable of developing tumors of particular interest in this experiment. No deleterious health effects and no tumors related to treatment were found in hamsters exposed to milled taconite ore containing fibrous-shaped particles of cummingtonite/grunerite, mineralogically related to amosite but in shorter lengths more comparable in size to fibers associated with drinking water supplies.