On the job lifting activities engaged in by nursing care workers were evaluated through observation of nursing personnel from several units of a hospital. The goal of the study was to investigate the importance of lifting behavior as a source of biomechanical stress. Of the 63 volunteers used for this study, seven were employed in the respiratory critical care unit (RCU), 19 in vascular surgical (V), 14 in the post anaesthesia recovery room (REC), 16 in orthopedics (ORTH), and seven in the delivery room (DEL). They were classified as registered nurses (RN) (47 subjects), licensed vocational nurses (LVNs) (nine), and orderlies (seven). A total of 3,131 lifts were monitored, with RNs performing 59 percent of them, orderlies 35 percent, and LVNs 6 percent. The length of time for each lift required from 1 to 2,700 sec, with an average of 21 seconds. Patient transfers accounted for 1,181 lifts and object transfers accounted for 1,946 lifts. A model of various factors which could be used to predict whether the person doing the lifting would ask for assistance during the lift was constructed using stepwise logistic regression analysis. Only in 15 percent of the observed lifts (466 lifts) was assistance of some kind sought by the lifter. Most of these assisted lifts involved the moving of a patient. The authors suggest that this may be due to the fact that patients are more irregularly shaped than other lifted objects. The level of work stress was also a factor associated with whether or not a lifter would seek assistance. In general, the higher the work stress involved, the more likely an individual would be to seek assistance. The number of preparations needed before a lift could be performed was another factor, as was the number of years of experience that an individual lifter had on the job. The authors recommend examination of psychological, social, and biomechanical factors in order to aid in control of low back injury.