© 2015: Servicio de Publicaciones de la Universidad de Murcia. Murcia (España). The increasing number of preterm babies in recent years has raised interest in studying the consequences of prematurity as a risk factor. In the present paper, 30 preterm babies (at 40 weeks of gestational age) were assessed using the Neonatal Behavioral Assessment Scale and the re-sults were compared with those of a control group of 28 full term babies. Moreover, the influence of weight, sex and gestational age was analyzed considering the Brazelton results in the preterm group. The preterm group showed significantly lower scores than the control group for 9 of the 28 behavioral items in the Scale and for 2 of the 5 clusters. However, preterm babies performed better in habituation to disturbing stimuli (light and noise) during sleep. In relation to the influence of sex, premature girls performed better in the Social-Interactive cluster. The preterm group has lower neurobehavioral conditions than the full term group, probably due to the abrupt interruption of their intrauterine maturation. In contrast, they showed a better ability of habituation, maybe as a consequence of a learning effect due to earlier additional extrauterine exposition. Key words: Neonatal Behavioral Assessment Scale; NBAS; prematurity; neonatal neurobehavior; neonatal development assessment.