An instrumental neutron activation analysis was applied to the multielemental analysis of the Stenopsyche griseipennis taken from the head water area and the lower of Tama river. The dry Stenopsyche griseipennis were irradiated for 3 minutes and 12 hours in a thermal neutron flux 1.5 X 10(12) n . cm-2 . sec-1 of TRIGA-II reactor of Rikkyo University. Thus, Al, Ca, Cl, Mg, V, Na, K, Br, La, Sm, Se, Cr, Ba, Cs, Sc, Rb, Zn, Co, Fe, and Sb could be analyzed. Analysis of the river water samples taken from the sampling points of the Stenopsyche griseipennis was carried out by the method given in the author's previous paper. The analytical results of Na, K, Zn and Se for the Stenopsyche griseipennis showed constant value independently of the river water quality, and Mn showed the different concentration between at the head water area and at the lower. On the other hand, the analytical results of Al, Fe, Sc, V, As, Sb, etc. showed wide range values. It can be considered that these elements were affected by taking up river sediment, and V, As and Sb concentrations in the Stenopsyche griseipennis at head water area showed larger values than those at the lower.