AbstractFriedreich ataxia (FRDA) is a progressive neurodegenerative disorder associated with ataxia, dysarthria, pyramidal tract signs, sensory loss, cardiomyopathy and diabetes. There is no cure for FRDA so far. Studies of the natural history of the disease and future therapeutic trials require development of appropriate outcome markers. Since any therapeutic benefit is expected to modulate deterioration over time rather than to reverse disability, potential outcome measures must be sensitive instruments carefully analysed for their significance. Clinical scales may represent an appropriate measuring tool. Over the last few years the construction, evaluation and validation of sensitive clinical scales for the assessment of disease severity and progression in ataxia have had considerable impact on our understanding of the disease. Currently, there are three different scales that are most frequently applied: The International Cooperative Ataxia Rating Scale (ICARS), the Friedreich Ataxia Rating Scale (FARS) and the Scale for the Assessment and Rating of Ataxia (SARA). All scales have been validated and compared with regard to their testing properties.