Rats were administered 288Pu or 239Pu nitrate either intramuscularly or by aerosol. Uptake from the site of injection was faster with 238Pu than with 239Pu, whereas the opposite process was noticed after inhalation. The respective bone burdens following intramuscular injection were of the same order provided they were related to the diffused fraction. The metabolic fate of both isotopes was different; there was greater early 238Pu urinary excretion. Following inhalation, 238Pu deposition in bone was higher. Treatment by DTPA was effective against 238Pu contamination.