Abstract: Environmental samples are dissolved in a concentrated HNO_3-HF-HClO_4 mixture. After addition of an appropriate quantity of a standard ~(242)Pu solution, each sample solution is purified by an anionic exchange resin column. The spiked samples are then fabricated into measuring specimens by rhenium filament carbonization technique and analyzed by isotope-dilution mass spectrometry (IDMS). The measurement results show that the procedure described in the present paper for analysis of plutonium by IDMS in environmental samples is feasible.