Study design:Review of the literature on the validity and reliability of assessment of spasticity and spasms.Objectives:Evaluate the most frequently used methods for assessment of spasticity and spasms, with particular focus on individuals with spinal cord lesions.Setting:Clinic for Spinal Cord Injuries, Rigshospitalet, University Hospital of Copenhagen, and Department of Medical Physiology, University of Copenhagen, Denmark.Methods:The assessment methods are grouped into clinical, biomechanical and electrophysiological, and the correlation between these is evaluated.Results:Clinical methods: For assessment of spasticity, the Ashworth and the modified Ashworth scales are commonly used. They provide a semiquantitative measure of the resistance to passive movement, but have limited interrater reliability. Guidelines for the testing procedures should be adhered to. Spasm frequency scales seem not to have been tested for reliability. Biomechanical methods such as isokinetic dynamometers are of value when an objective quantitative measure of the resistance to passive movement is necessary. They play a minor role in the daily clinical evaluation of spasticity. Electrophysiological methods: These techniques have provided valuable insight to the pathophysiological mechanisms involved in spasticity, but none of these techniques provide an easy and reliable assessment of spasticity for use in the daily clinic.Conclusion:A combination of electrophysiological and biomechanical techniques shows some promise for a full characterization of the spastic syndrome. There is a need of simple instruments, which provide a reliable quantitative measure with a low interrater variability.