A high percentage of musculoskeletal disorders in nursing staff with the task of patient lifting is reported in the literature. These disorders are considered to be of multiple etiology and attempts have been made not only to assess the physical load but also to identify the direct or indirect influence of organisational and psychosocial factors so that preventive measures be more appropriate and effective (Law 626/94). In this context, in a recent publication NIOSH recalled that psychosocial factors can alter the relationship between exposure to physical loads and the development or the prognosis of these disorders, and stresses that understanding these relationships is the crucial factor in assessment of exposure that can be addressed with preventive and therapeutic measures. A study was carried out on the staff (113 subjects) of a large hospital in northern Italy with departments recognised by certified occupational physicians as at risk for the musculoskeletal apparatus. In order to quantify the working conditions and the disorders of the spine, a protocol proposed by the Ergonomics of Posture and Movement Research Unit of Milan University was further developed and validated. For assessment of psychosocial factors an Italian version of R. A. Karasek's "Job Content Questionnaire" was drawn up and validated by the Centre for Study and Research of Chronic Degenerative Diseases in Working Environments of Milan University. In addition, Borg's Scale was used for perception of physical load, Kurimori and Kakizaki's Scale for mental fatigue, Kjellberg and Iwanowski's Scale for states of stress, plus the Maslach burnout inventory. Nonparametric statistical analysis was applied to determine the influence of physical and organisational and psychosocial factors on disorders of the musculoskeletal apparatus. The results confirm a good agreement between the objective and subjective assessments of "manual patient handling" risk (Kendall p from 0.26 to 0.37, p > 0.001) and the significant relationships between psychosocial factors and disorders of the lumbar region of the spine: past history of episodes of acute low back pain is associated with limited possibility of making independent decisions (U-Mann Whitney z = 2.81, p 0.004) and job insecurity (U-Mann Whitney z = -2.36, p 0.01); episodes of acute low back pain above the threshold in the previous year were associated with low discretionary powers at work. The results will be discussed on the basis of the possible prevention measures.