OBJECTIVES:The assessment of early sucking by preterm infants provides information on the ability of these infants to efficiently and safely receive nutrients via an oral route (oral feeding). To analyze the application and reliability of an instrument in assessing non-nutritive sucking that indicates a capacity for oral feeding in the routine care of different neonatal units. METHODS:A multicenter, prospective cohort study was conducted in seven neonatal units. A non-nutritive sucking assessment with a formulary validated by Neiva et al (2008) (variables evaluated: rooting reaction; easy initiation of sucking; labial sealing; tongue central groove; peristaltic tongue movements; jaw raising and lowering movements; labial, tongue and jaw coordination; sucking strength; sucking rhythm; bites; excessive jaw excursion; stress signals) was applied to 199 pre-term newborns, who had a chronological age$2 days and were clinically stable. These infants were divided into two groups based on their corrected gestational age at the first assessment, as follows: Group I-infants with a gestational age#33 weeks and Group II-infants with a gestational age between 34 and 36 6/7 weeks. RESULTS:The mean gestational age was 31.66¡2 weeks, and the mean birth weight was 1494¡373 g. The mean scores on the non-nutritive sucking assessment were 46¡25 in Group I and 49¡24 in Group II. The beginning of oral feeding was successful in 43 (67.2%) infants in Group I and 64 (81%) infants in Group II (p= 0.089). CONCLUSION:The method identified preterm infants who were able to feed orally based on 33 points in the non-nutritive sucking assessment and a corrected gestational age of 32 weeks or more. The corrected gestational age was the most important factor in predicting the success of oral feeding.