There is no validated method of measuring spasticity per se The most widely accepted clinical scale, the modified Ashworth scale, has been evaluated only at the elbow and does not take account of the possible effects of posture and associated reactions on tone. The aim of this study was to develop a reliable measure which incorporated response to passive movement, resting posture and associated reactions to active effort. The Tone Assessment Scale was constructed and modified, and its reliability tested in 15 patients with stroke. Inter-rater comparisons were made between two physiotherapists examining the reliability of each item of the scale. The six items reflecting response to passive movement were reliable (Kw 0.66 – 0.94), while those relating to posture were not (K 0.12 – 0.49). Only two of the three items relating to associated reactions were reliable (Kw 0.79 and 0.94, K 0.31). The establishment of reliability of measurement of tone at a number of joints should ensure more comprehensive estimates of spasticity and facilitate determination of treatment effects.