The uptake of tritium by tungsten and its release behavior have been investigated. Specimens annealed at 773 K, 873 K, 973 K, 1,073 K and 1,173 K for 3 hours and loaded with tritium at 773 K for 3 hours accumulated 0.125 ppm, 0.068 ppm, 0.067 ppm, 0.038 ppm and 0.033 ppm, respectively (tritium solubilities were 3.6x 10-9 at.fr.Pa-1/2, 2.0x 10-9 at.fr.Pa-1/2, 1.9x 10-9 at.fr.Pa-1/2, 1.1x 10-9 at.fr.Pa-12/ and 9.7x 10-10 at.fr.Pa-1/2, respectively). The difference is attributed to the existence of trapping sites or oxide films.