RESEARCH IN OUR LABORATO-RIES 1 " 4 during the past 5 years has resulted in the isolation, characterization, and development of zirconium silicate, an insoluble inert abrasive, as an improved cleaning and polishing agent for the oral hard tissues. However, during the past 10 years several reports have appeared in the literature relative to the formation of granulomas and a peculiar granulomatous hypersensitivity associated with the use of specific soluble zirconium salts. This paper reviews these reports and in addition presents laboratory findings when zirconium silicate is examined under comparable conditions.Weber and coworkers 5 noted the occurrence of axillary granulomas in a 37 year old woman who used an underarm deodorant containing sodium zirconium lactate as the active agent. The clinical appearance of the granuloma was fairly firm, rounded, multiple papules 2 to 4 mm. in diameter. The papules were dark red and located predominately in the dome of the axilla. The growth of hair was unaffected and the clinical manifestations of the lesion were not troublesome to the subject. Histologic examination revealed a dense granulomatous infiltrate, consisting of epitheloid cells, Langhan's giant cells, and lymphocytes forming numerous tubercles. Polariscopic examinations were negative for the presence of foreign bodies. A slow, spontaneous