[en] Described and discussed are experimental studies conducted by author's group using a body phantom to measure the effective dose to astronauts in Russian space station of ninth Shuttle-Mir Mission (STS-91). The studies are the first investigation done by the actual measurement of the dose in space, which has been estimated by calculation hitherto. The dosimeters for tissue/organ were Mg₂SiO₄:Tb TLD (MSO, Kasei Optonix) and CR-39 PNTD (HARZLAS TD-1, Fukuvi Chem. Ind.). MSO was used on basis of the previous examination of its response giving the desirable relationship between relative TLD efficiency and linear energy transfer (LET) using Heavy Ion Medical Accelerator in Chiba (HIMAC) heavy ion beams and PNTD, also giving the suitable relationship between the beam incidence angle and track-formation sensitivity and between the latter and LET. Fifty nine dosimetric units of Tough Water Phantom (Kyoto Kagaku) having 3 MSO elements and 2 PNTD tips were placed in the defined organ positions of RANDO body phantom (Alderson Res. Lab.), which was then fixed at a rack in the space shuttle Discovery. The Discovery launched on June 2 to dock with the Mir and returned on June 12, 1998 (9.8-day flight) and the body phantom was analyzed in Japan. For the skin, thyroid, bone surface, esophagus, lung, stomach, liver, bone marrow, colon, bladder, testicle, mammary gland and others, analyzed and calculated were absorbed dose (mGy) and tissue equivalent dose (Ht, mSv) with use of International Commission of Radiological Protection (ICRP) factors (1990) of effective quality and tissue weighting. Mean effective dose was found to be 4.1+/-0.22 mSv and dose rate, 0.4 mSv/d. No significant difference was found between Hskin and Ht in radiation sensitive, deep tissues like lung, stomach, gonad and breast, suggesting the exposing contribution of high energy neutron yielded within the body. As well, it was suggested that personal exposure dose of astronauts was measurable by dosimeters put on the positions like breast and abdomen as similar to radiation workers on the ground. (R.T.)