Purpose: This study was done to determine whether providing auditory and vestibular stimulation to preform infants would have an effect on stress hormones. Methods: The design was a nonequivalent control group protest-posttest design in a quasi-experimental study Seventy-nine preform infants were assigned either one of two experimental groups or to a control group: 27 in the auditory stimulation group, 25 in the vestibular stimulation group and 27 in the control group. The criteria for inclusion in this study were 1) gestational age of less than 37 weeks, 2) birth weight of less than 2,500g, 3) the absence of congenital anomalies or specific diseases, 4) recovering physiological weight loss, and 5) weaned from ventilatory assistance or oxygen. The data were collected from March 2002 to May 2003. The auditory stimulation, a music audiotape, was provided 20 minutes twice a day for 10 days and the vestibular stimulation, an infant waterbed, was provided for 10 days. On day 1 and day 10 of the study, 24 hour urine sample was collected for norepinephrine, epinephrine, and cortisol assays. In the data analysis SPSSWIN 10.0 program was utilized for descriptive statistics, ANOVA and t-test. Results: General characteristics of the three groups showed no significant differences, thus three groups were found to be homogenous. The 24 hour urine cortisol for the auditory (t=3.489, p=.001) and for the vestibular (t=2.638, p=.013) stimulation group were significantly reduced compared to the control group after 10 days. Conclusions: The results suggest that auditory and vestibular stimulation can be used to reduce 24 hour urine cortisol in preform infants. Therefore, music audiotapes and waterbeds provided in incubator are be recommended for reduction of the stress in preform infants who are hospitalized in neonatal intensive care units.