Abstract The aim of this preliminary study was to investigate sleep-wake rhythm in active, healthy elderly people residing in their usual habitat. The subjects were thirty-five male volunteers within an age range of 65–95 for 3–4 days. We measured the sleep-wake rhythm of the subjects with an Actillume® which is a combined wrist activity monitor and illumination recorder. Analysis of the Actillume® recording showed that 24 of the 35 subjects (69%) kept continuous activity indicating good maintenance of wakefulness with high light exposure. The mean mesor of sleep-wake rhythm, however, significantly decreased in the older subjects (aged 80–95; n= 15).