PURPOSE: The study aimed to compare the physical activity of hematopoietic stem cell transplantation (HSCT) patients with healthy people (HP). METHODS: The research design of this study was cross sectional and, descriptive study. It was conducted from January 26th to May 22nd, 2013. We matched HSCT patients to HP based on age and gender, and measured physical activity using a pedometer. Patient's clinical information were gathered by the medical record reviews. RESULTS: The number of steps was significantly less in HSCT patients (HSCT: 214 (7~3,373) vs HP: 7,921 (3,180~17,539), p<.001). Physical activity time was significantly less in HSCT patients (HSCT: 840 (680~1,320)min vs HP: 990 (540~1,090)min, p<.001). Step count showed a significant relationship with platelet count (r=.40, p=.004). CONCLUSION: HSCT patients perform very low intensity of physical activities. The study shows the necessity to apply programs to promote physical activities in isolation rooms for patients undergoing HSCT.