Effects of pressure up to 1.5 x 10(8) pascal on the structure and function of endoglucanase was studied. When the enzyme was pressurized at 1.5 x 10(8) pascal for 1 h at 20 degrees C, the enzyme remained its activity on release of pressure, but its pH-activity and temperature-activity curves are different from that of the native enzyme and the half-life at 50 degrees C was elongated about onefold. alpha-helex content of the enzyme and the number of tryptophan residue on the surface of enzyme molecules were increased. After the enzyme was compressed at 4.5 x 10(7) pascal for 9 h, the enzyme remained its activity, whereas its structure was nonreversibly changed.