This thesis reviews the literature on the development of infant sleep to establish whether relevant criteria for planning primary preventive intervention of infant sleep disturbance (ISD), derived from Mrazek and Haggerty's (1994) criteria for evaluating prevention interventions, have been met. It concludes that the methodological and conceptual limitations of this literature have prevented the two most critical criteria from being met. These are, when preventive intervention should occur, and what specific infant and parent factors should be targeted. In order to address these criteria a prospective longitudinal repeated measures design was employed. Parents of 75 normally developing infants, 52 from the age of 1 month, and 23 from the age of 2 months completed sleep diaries for six consecutive days, each month until the infant had reached 12 months of age. All night, infra-red, time-lapse video recording (TLVR) was also obtained for the purpose of reliability. There were two separate studies. The first challenged traditional definitions of sleeping through and demonstrated an 8 hour criterion to be behaviourally meaningful and developmentally realistic. It then investigated the norms for this developmental task. The results indicated the optimal time for prevention to be within the first 2 months. By six months two discrete group of infants were identified, one group with emerging sleep disturbance and the other demonstrating settled sleep. Stability in infants' relative sleep scores was demonstrated across the first 12 months although many parents intervened. The second study tested the predictions from a developmental model (France & Blampied, 1999) which suggested the proximal parent and infant risk factors that precede and predict lSD. At 1 month a discriminant function analysis identified 3 variables that correctly classified 90.4% of the infants into either a group of infants with emerging sleep disturbance or a group without sleep disturbance at 6 months of age. Two of these 3 variables also predicted group membership at 12 months. This research has filled some critical gaps in the research base by identifying parent and infant factors to be targeted, and the optimal time for prevention. It empirically supports and extends the developmental model, thereby providing a framework for planning primary prevention of ISD. Several directions for future research are presented.