This study evaluated the sleep/wake cycle of individuals with asthma in relation to asthma control, daytime sleepiness, and daytime activity. Ten persons with mild to moderate persistent asthma monitored their sleep quality and daytime wakefulness for 7 consecutive days using 24-hours wrist actigraphy. Degree of asthma control strongly correlated with sleep quality. Individuals whose asthma was not well controlled took longer to fall asleep, awoke more often, and spent more time awake during the night compared to those with well controlled asthma. Poor asthma control, use of rescue medications, and asthma symptoms were associated with daytime sleepiness and limitations in physical activity and emotional function. Forty percent of subjects reported clinically significant daytime sleepiness. Evaluating asthma throughout a 24-hour cycle provides valuable information on variations in the sleep/wake cycle associated with asthma control, use of rescue medications, and asthma symptoms.