The human neonate normally spends nearly 2/3 of its time asleep, and of this time ca 2/3 are spent in active sleep (AS). The present study was designed to investigate the temporal organisation and behavioural composition of this state. The hypothesis was put forward that the amount of facial behaviour that could be observed at any point in time during AS was representative of the neonate's general state of activation, and that the degree of activation varied with cyclic regularity. To test this, the facial behaviour of 8 normal neonates was filmed, and the films observed repeatedly. All activity occurring in three facial regions was registered and the resultant behavioural sequences analysed. It was found that facial behaviour tended to occur in bursts, and the median activity-quiescence cycle length was about 9 seconds. The amount of facial behaviour tended to wax and wane in a compound rhythm, and the lengths of the activity cycles involved could be predicted from a geometric function model. The results were compared with the evidence for cyclic behavioural activity found by previous investigators, and several explanatory models were examined. It is proposed that the activity cycles observed here are related to the rhythmicity observed in other behavioural states of the human infant.