[en] Rats and beagles were exposed by inhalation to an aerosol containing stable Sm₂O₃ tagged with ¹⁴⁵Sm₂O₃ and ¹⁴³Pm₂O₃. The animals were sacrificed at 0, 14 and 30 days post-exposure to compare the kinetics and translocation of ¹⁴⁵Sm and ¹⁴³Pm. Quantitative analysis for ¹⁴⁵Sm and ¹⁴³Pm in several tissues and excreta indicate that the two rare-earth elements were mobilized and distributed similarly by the rats and dogs. Results indicate that within the error of the measurement technique, samarium acts as a carrier for promethium. The data also indicate that activities measured in faecal samples could be used to predict lung burdens of ¹⁴⁷Pm. At activity levels and sintering temperatures employed in the rat exposures, there was sufficient activity in urine samples to permit its use as an indicator of lung burdens of ¹⁴⁷Pm. At activity levels and sintering temperatures employed in the dog exposures, this was not the case. (author)