The effect of ageing on the contractile properties of the first dorsal interosseous muscle was investigated. A group of 42 healthy male subjects between the ages of 10 and 80 years took part in the study. The time to peak tension was significantly prolonged with increasing age but no evidence was found of an extension of the half relaxation time. When left and right hands were compared no significant differences were found. The results are discussed in relation to the changes previously observed in ageing muscle and may indicate a general age change of the muscle or the loss of faster twitch fibres.