This study explores the duration and timing of day time waking periods required for sleep disturbed infants to improve day and night sleep. Seventy-nine sleep disturbed outpatients with day and night sleep problems were investigated before and two weeks after a brief sleep intervention. Data were collected by interviewing parents on their infants' day and night sleep patterns. Besides instructing the parents on night sleep regulation, they were advised to regulate day sleep. After the intervention, duration of day and night sleep increased and frequency of night waking decreased. The mean duration of the first waking period in the morning did not change, but the range decreased. The mean duration of the last waking period in the evening increased. The frequency of short and irregular day naps and the need for assistance in falling asleep decreased after the intervention. It is recommended that the last waking before night sleep is lengthened to reduce day and night sleep problems.