Rates of wrist activity and yawning were recorded continuously for 7-15 days in adult human male and female subjects. In the 15 min following 747 yawns wrist motion increased reliably in all subject records. The data were consistent with an hypothesis that yawning is predictive of an increase in activity level. In a second study, data from daily logs kept by 45 subjects confirmed previous findings that yawning frequency is unrelated to prior amount of sleep, or to times of awaking or retiring. More yawning occurred during the week than during weekends.