The development of a new scale to measure somatic and autonomic perception, the Modified Somatic Perception Questionnaire or MSPQ is described. It has been derived specifically for use with chronic backache patients, although its utility with other chronic pain problems is currently under investigation. Following pilot studies on anxious patients and normal controls a pool of items was subjected to reliability checks and parallel-form analysis. The final 13 item scale was derived from a pilot study of 102 chronic backache patients and its construct validity confirmed on a further study of 200 backache patients. Sex differences in the use of the scale were integrated into the final version. The scale was compared with the Zung Depression Inventory and the first three clinical scales of the M.M.P.I. Individual items were compared with clinical symptomatology rated independently by an orthopaedic surgeon. In a small experimental study the MSPQ was compared with electromyographic readings from the erector spinae muscles and biceps, with the rating of pain using the McGill Pain Questionnaire, and with experimental ischaemic pain using the submaximum effort tourniquet test. In other studies the scale has been shown to be of importance in the understanding of functional disability. Its predictive validity in response to treatment is currently under investigation in studies of spinal fusion, chemonucleosis and multidisciplinary pain programmes. The simple 13 item four-point self-report scale is easy to administer, has high patient compliance and, in conjunction with measures of depressive symptomatology and inappropriate signs and symptoms would seem to be of considerable promise in the understanding of the sequelae of backache and much more sensitive than traditional measures of personality structure.