OBJECTIVE:To establish the variability of fast testing velocity and joint range of motion and position when assessing lower-limb spasticity in individuals following neurological injury. DESIGN:Observational study of people with lower-limb spasticity. SUBJECTS:Patients with an upper motor neurone lesion (n = 35) and clinicians experienced in spasticity assessment (n = 34) were included. METHODS:The Modified Tardieu scale (MTS) was completed on the quadriceps, hamstrings (2 positions), gastrocnemius and soleus for each participant's more affected lower limb by 3 assessors. Mean absolute differences (MADs) were used to calculate variability as a measure of reliability. RESULTS:Variability of peak testing velocity was greater at the ankle joint compared with the knee joint. The greatest MAD for V3 (fast) inter-rater testing velocity was 119°/s in the soleus, representing 29.4% of the mean variable value, and least for the quadriceps (64.3°/s; 18.5%). Inter-rater variability was higher than intra-rater variability for all testing parameters. The MAD for joint end angle ranged from 2.6° to 10.7° and joint start angle from 1.2° to 14.4°. CONCLUSION:There was a large degree of inter- and intra-rater variability in V3 testing velocity when using the MTS to assess lower limb spasticity. The inter-rater variability was approximately double the intra-rater variability.