The purpose of this investigation was to determine, in part or full, the physiological response of experimental animals to the purified and technical grades of ciphenyl. The observations concerned themselves with the mode of local and systemic action, the degree of toxicity, and the gross and microscopic effects of these compounds upon various tissues following the administration of single lethal and repeated sublethal doses of individual members of the group. Furthermore, it was considered desirable to study in some detail the effect of these compounds upon the concentration of urea nitrogen, prothrombin, and hemoglobin in the blood, upon the formed elements in the blood, and upon the excretion of hexuronates and sulfates in the urine.