Thirty patients with spinal cord injury (SCI) were randomly selected to participate in this study which evaluated the inter rater reliability of the original and of the modified Ashworth scale for the assessment of spasticity in the lower limbs. A doctor and a physiotherapist rated the muscle tone of hip adductors, hip extensors, hip flexors and ankle plantarflexors according to the original and to the modified Ashworth scale. The results were analyzed using a Cohen's Kappa statistical test and showed varying levels of reliability for different muscle groups and limbs. Kappa values ranged between 0.21 and 0.61 (mean 0.37). The original scale was slightly more reliable than was the modified scale. However, this difference was not significant (P > 0.05), and was not consistent between the two limbs and between different muscle groups. It was concluded that the Ashworth scale is of limited use in the assessment of spasticity in the lower limb of patients with SCI. Further work is required to establish a standardised speed of muscle stretching during the test, or to find more appropriate grades and descriptions of spasticity for this patient group. The effects of training of the raters in the use of the scales also warrants further investigation.