The purpose of this study was to identify the effects of breathing biofeedback training on the stress of nursing students in clinical practice. The research design was a nonequivalent control group pretest-posttest design. The subjects of this study were 39 nursing students from the College of Nursing of K University. The study was conducted from July 20 to September 3, 1998. The subjects were assigned to one of two groups : the experimental group (19 students), and the control group (20 students). The breathing biofeedback training was performed 12 times with the experimental group. The level of psychological stress was measured using the State Anxiety Inventory, Profile of Mood State, and Visual Analogue Stress Scale. The level of physiological stress was measured using pulse rate and blood pressure. The data were analyzed using descriptive statistics, $x^2-test$, t-test, and repeated measures of ANOVA. The results of study are as follows : 1) State anxiety scores were not significantly different between the experimental group and the control group after the biofeedback training. 2) Profile of mood state scores were not significantly different between the experimental group and the control group after the biofeedback training. 3) Visual Analogue Stress Scale scores were significantly different between the experimental group and the control group after the biofeedback training(F=11.68, p=0.002). 4) Pulse rates were not significantly different between the experimental group and the control group after the biofeedback training. 5) Systolic blood pressures were significantly different between the experimental group and the control group after the biofeedback training(F=5.44, p=0.025). 6) Diastolic blood pressures were not significantly different between the experimental group and the control group after the biofeedback training. On the basis of the above findings, the following recommendations for further study are made ; 1) Identification of the effects of breathing biofeedback training at times of high stress during clinical practice. 2) Identification fo the effects of stress reduction according to the frequency of the breathing biofeedback training.