Two groups of infants (40 normal full-term, 24 prematurely born infants) were matched on conceptional age and were studied at seven ages during the first year of life. All-night time-lapse video somnography was obtained n the home at 2, 4, 8, 20, 24, 36, and 52 weeks of age. The developmental course of sleep-wake state proportions, sleep onset indices, and special variables assessing temporal organization are compared. Age-appropriate developmental norms for sleep-wake state assessment during the first year of life are presented, using video somnography. In general, sleep-wake state ontogenesis is comparable in the two groups. The premature group is more variable from one age to the next, even though both groups demonstrate significant individual stability of some sleep-wake variables over the first year of life.