The regain of independent ambulatory ability is a important goal in the rehabilitation program of hemiplegic patient. Not only the function of lower extremity muscles, but also trunk muscles which stabilize extremities and pelvis, are important factors in normal gait. Therefor, it is necessary to develop an effective program which can improve muscle strength and symmetric activity of trunk muscles. The purpose of this study was to evaluate the influence of trunk muscle strengthening by forceful respiratory exercise on the gait asymmetry ratio in hemiplegic patient. 45 Hemiplegic patients due to stroke was randomized in 3 groups, forceful expiratory training(FET), forceful inspiratory training(FIT) and control group. In the experimental groups, ordinary physical therapy with forceful expiratory training and forceful inspiratory training for 20 minutes duration 3 times per week for 6 weeks were respectively performed. In the control group, only ordinary physical therapy was done. Before and after experiments, temporal-spatial gait parameters was measured in all patients. The data of 28 patients who carried out the whole experimental course were statistically analysed. The results of these experiment are as follows : 1. In comparison of difference of single support time asymmetry ratio among 3 groups, the FET group was significantly decreased than the control group (p<.05). 2. In comparison of difference of step length asymmetry ratio among 3 groups, the FIT group was significantly decreased than the control group (p<.05). Based on these results, it is concluded that the forced respiratory exercise program for 6 weeks can be improve the gait asymmetry ratio in hemiplegic patients. Therefore, the forced respiratory exercise is useful to improve the walking ability in hemiplegic patients. Since this study dealt only with the patients who could walk more than 3 meters in distance on floor independently, the further study for evaluating the influence of the forceful respiratory exercise on patients with acute stage stroke and also the development in various methods of use are expected.