T-lymphocytes were determined by rosette formation with sheep erythrocytes in the peripheral blood obtained from 30 healthy aged subjects who were practicing Taichiquan (88 style) exercise and 30 age-matched normal aged who served as a control group. At rest the total number of T-lymphocytes and the number of active T-lymphocytes were increased significantly in the exercise group compared with the controls. Immediately after a bout of Taichiquan exercise, a marked increase of active T-lymphocytes occurred. In conclusion, the results indicate that frequent Taichiquan exercise causes an increase of T-lymphocytes in the blood.