In order to investigate of the effects of rapid rotating shift work on physiological stress, the activities of urinary Na+, K+, Cl- were measured in 14 rotational shift nurses, during day shifts(8AM-4PM, n=4), evening shifts(4PM-12MN, n=5), and night shifts(12MN-8AM, n=5) in hospital twenty students attending nursing college a used as control group. Urine specimens were collected in 30 minutes before and after work on the second day of shift work. In day shift nurses, Na+ activity was 137mM at 8AM and increased to 206mM at 4PM, whereas K+ activity was 42mM at 8AM and no significant change at 4PM. Cl- activity was changed from 234mM to 344mM at 4PM at 8AM. In the evening shift, Na+ activity was 117mM at 4PM and 140mM at 12MN, K+ activity was 22mM and 32mM, respectively. Cl- activity was 169mM and changed to 270mM. During the night shift, Na+ activity was 128mM at 12MN and changed to 161mM at 8AM, K+ activity was 42mM at 12MN and 8AM, and Cl- activity was from 303mM and changed to 355mM. In general, the urinary ion activities seemed to increase after work, however there were no significant changes in ion activities except the Na+ increase in day shift. The mean of the activities of K+ and Cl- before and after work during the day and night shift were significantly higher than those in control group(P<0.05). K+ activities were also higher than that of evening shift(P<0.05). However, there was no difference in Na+ activity among the control group and three shifts. There was a significant relationship among urinary Na+, Cl- and K+ in the control group and rotating shift nurses except between Na+ and K+ in shift. The relationship between Na+ and Cl- was low in shift work and there was no significant relationship between Na+ and K+ in shift, suggesting that the active regulation K+ and/or Na+ in response to stress upon the shift work disrupted the ratio of urinary Na+ to K+ and also lowered the relationship between K+ and Cl-. These results suggest that nurses working the day shift were overloaded and under stress, and the night shift interfered with the physiological rhythm of the nurses.