The Objectives of this research is to determine the effect of aerobic exercise program on health status and physical fitness in patients after the stem cell transplantation. This research design is one-group pretest-post test design. Sixteen subjects were selected from one university hospital in Seoul for the study, they was carried out aerobic exercise three to five times a week for 12 weeks. The period of data collection was from February to July, 2000. The collected data was analysed by descriptive analysis, paired t-test, content analysis SAS program was used for the statistical analysis. The results are as follows : 1. There was a significant improvement in the Physical functioning, Vitality and Reported change (t=2.39, p=0.03; t=2.35, p=0.03; t=2.58, p=0.02) but no change was observed in the Role physical, General health perception, Bodily pain, Social functioning, Role emotional and Mental health. 2. There was a significant improvement in the physical fitness (higher VO2 max, t=2.43, p=0.02; lower systolic pressure, t=-4.09, p=0.001; lower diastolic pressure, t=-3.43, p=0.002; lower pulse rate, t=-3.43, p=0.004; higher muscle sustaining power, t=2.79, p=0.015; higher muscle power, t=5.18 p=0.000; higher power of beginning, t=5.55, p=0.001; higher the sense of equilibrium, t=3.57, p=0.003; higher Hemoglobin, t=5.92, p=0.000; higher Hematocrit, t=5.38, p=0.000). Therefore, this study will provide a theoretical back ground for patients after stem cell transplantation to understand the importance of physical exercise and maintain physical exercise; and for other researches to refer to the results for exercise protocol of rehabilitation program.