BACKGROUND High-flow nasal cannulae (HFNC) are gaining in popularity as a form of non-invasive respiratory support for preterm infants in neonatal intensive care units around the world. They are proposed as an alternative to nasal continuous positive airway pressure (NCPAP) in a variety of clinical situations, including post-extubation support, primary therapy from birth and 'weaning' from NCPAP. OBJECTIVES To present and discuss the available evidence for the use of HFNC in the preterm population. METHODS An internet-based literature search for relevant, original research articles (both randomised studies and not) on the use of HFNC in preterm infants was undertaken. RESULTS A total of 19 studies were included in the review. Distending pressure generated by HFNC in preterm infants increases with increasing flow rate and decreasing infant size and varies according to the amount of leak around the prongs. HFNC may be as effective as NCPAP at improving respiratory parameters such as tidal volume and work of breathing in preterm infants, but probably only at flow rates >2 litres/min. The efficacy and safety of HFNC in preterm infants remain to be determined. CONCLUSIONS There is growing evidence of the feasibility of HFNC as an alternative to other forms of non-invasive ventilation in preterm infants. However, there remains uncertainty about the efficacy and safety of HFNC in this population. Until the results of larger randomised trials are known, widespread use of HFNC to treat preterm infants cannot be recommended.