Cyclotriphosphazene (CTP) ester is one of a series of compounds developed for use as a fire-resistant hydraulic fluid. The most significant routes of industrial exposure to hydraulic fluids are dermal, because of spills or leaks, and aerosol inhalation from pressurized system leaks. This study was designed to evaluate the toxic effects associated with repeated or continuous exposure to CTP by both dermal and inhalation routes. Male and female Fischer 344 (F-344) rats were exposed for 3 weeks to air alone, or to 0.25, 0.50, or 1.00 mg CTP/L. No deaths or signs of toxic stress occurred during the exposure period. A depression in mean body weight gain and increases in numbers of pulmonary alveolar macrophages and renal hyaline droplets were noted in both genders. Male and female New Zealand White (NZW) rabbits were treated dermally for 3 weeks with mineral oil, or 0.25, 0.50, or 1.00 g CTP/kg. No toxic effects were noted in either gender of rabbits.