This is the "rst of two articles to report a biomechanical evaluation and psychophysical assessment of nine battery-powered lifts, a sliding board, a walking belt, and a baseline manual method for transferring nursing home residents from a bed to a chair. The objectives of the biomechanical evaluation were: (1) to investigate the e!ects of transfer method and resident weight on the biomechanical stress to nursing assistants performing the transferring task, and (2) to identify resident-transferring methods that could reduce the biomechanical stress to the nursing assistants. Nine nursing assistants served as test subjects; two elderly persons participated as residents. A four-camera motion analysis system, two force platforms, and a three-dimensional biomechanical model were used to measure biomechanical load. The results indicate that transfer method and resident weight a!ect a nursing assistant's low-back loading. The basket-sling and overhead lift devices signi"cantly reduced the nursing assistants' back-compressive forces during the preparation phase of a resident transfer. In addition, the use of basket-sling, overhead, and stand-up lifts removed about two-thirds of the exposure to low-back stress (lifting activities per transfer) as compared to the baseline manual method. Thus, the use of these devices reduces biomechanical stress, and thereby will decrease the occurrence of resident-handling-related low-back injuries. Furthermore, lifting device maneuvering forces were found to be signi"cantly di!erent and a number of design/use problems were identi"ed with various assistive devices. The second article will detail the psychophysical assessment of the same resident-transferring methods. Published by Elsevier Science Ltd.