Measures derived from the wrist actigraph have been found to correlate highly with EEG measures of normal sleep. Although the actigraph has been used to study normal sleep, few studies have used the actigraph as a measure of sleep of elderly insomniacs. The present study, which used elderly insomniacs, sought to investigate the sensitivity of the actigraph to detect the effects of an insomnia treatment. The actigraph was sufficiently sensitive to detect the effect of the sleep restriction therapy used on several sleep measures. Subsidiary analyses suggested that the sleep log, although not an accurate measure of sleep, may be useful as a measure of elderly insomniacs' subjective perception of sleep. Because the actigraph can be used more easily and less expensively than the polysomnogram, the actigraph appears to be a promising measure for assessing the efficacy of treatment interventions in elderly insomniacs.