The aim of the study was to construct an observation instrument for description and assessment of nursing personnel's work technique in patient transfer tasks with regard to musculoskeletal health and safety, and to evaluate the validity and reliability of the instrument. The instrument consists of 24 items arranged in three phases of a transfer: the preparation phase, the starting position and the actual performance. Observations are made from video recordings. A detailed description of the individual's work technique, including actions taken to prepare the transfer, the interaction with the patient and any assistant co-worker, and the motor performance of the nurse, is provided. An attempt was made to quantify the assessments, by calculating an overall score of the work technique with regard to the level of musculoskeletal hazard and safety. The validity and reliability of the instrument were evaluated on 35 video-recorded patient transfers from hospital wards. The validity and reliability were mostly satisfactory, both when evaluating the agreements between the observations of each item (i.e. values '0.40), and when evaluating the agreements between the overall scores (i.e. intraclass correlation coe$cients 0.71}0.90). Further improvements to enhance the agreements are suggested.