It was found that the smallest dosage of beryllium oxide dispersions inducrng death in rats, when injected subcutaneously, was 10 mg/kg of weight. The toxicity of beryllium oxide, under these conditions, approached that of beryllium chloride, beryllium nitrate, and beryllium oxifluoride. i.e., the soluble compounds. The toxicities of various subcutaneously or intravenously injected beryllium compounds are tabulated. When inhaled, beryllium acetate is lethal to white rats at a concentration of 30 mg/m/sup 3/ of air. It is concluded that the toxicity of insoluble beryllium salts, including the oxide, greatly increases with the degree of dispersion. (auth)