ABSTRACT: Background: Although both expectant mothers and expectant fathers complain of fatigue during the last trimester of pregnancy, studies have focused exclusively on mothers. This pilot study examined parents' levels of morning or evening fatigue, number of uninterrupted sleep periods and length of sleep during the last trimester of pregnancy; and the relationship of sleep to parents' reports of fatigue. Methods: Data were collected from 24 midwestern, nulliparous couples, who completed the Visual Analog Scale for Fatigue each morning and each evening on 4 consecutive days during the last trimester. Concurrently, the couples recorded sleep and wake periods in an activity diary. Results: Expectant mothers but not expectant fathers reported increasing levels of fatigue, especially morning fatigue, as the pregnancy progressed. Expectant fathers and mothers did not differ either in the night-time mean number of minutes of sleep obtained, or in the mean number of night-time uninterrupted 90-minute sleep cycles obtained. Fatigue and sleep were not significantly related for either mothers or fathers, Conclusions: These findings support the multidimensional nature of fatigue and indicate a need for perinatal health care givers to develop individualized interventions for mothers during the last trimester of pregnancy. Fathers should also participate in future research of factors influencing the prenatal and postpartum experience.