In this study 17 male and 13 female infants with gestational ages between 27 and 34 weeks (mean 30.7) and birthweights between 750 and 2020g (mean 1545) were evaluated with the Brazelton Neonatal Behavioral Assessment Scale at 35, 38, 40 and 44 weeks postconceptional age. All were in room air at the time of observation and none was being treated with mechanical ventilation. In the motor performance cluster, all five items improved with advancing postconceptional age and in the orientation cluster four of six items improved with age: these show better behavioural evolution compared with other clusters. There was no change in auditory response, with good response from 35 weeks onward. Behavioural development did not proceed evenly in all areas, and within the same cluster certain features developed earlier than others. From 35 to 44 weeks, auditory responsiveness was similar to that of previously evaluated healthy term infants.