Gastric emptying (GE) is difficult to evaluate properly in preterm infants because of the lack of safe and reliable noninvasive methods. The 13C-octanoic acid breath test, a noninvasive method to assess GE, was validated in adults. The aim of this study was to adapt the methodology of the 13C-octanoic acid breath test regarding test meal and sampling methods and to define normal values for healthy preterm infants. We tested 11 clinically stable preterm infants who demonstrated normal fetal growth. The infants mean gestational age at birth was 33 weeks, mean birth weight was 1754 g, mean postnatal age at the day of study was 26 days, and mean weight was 2296 g. After a fasting period of 3 h, the subject was fed a test meal with low and stable 13C background activity mixed with 50 microliters of 13C-labeled octanoic acid and 1 g polyethylene glycol 3350. Breath samples were collected using a nasal prong in basal conditions and after the test meal. CO2 production according to weight and age was used in the calculations for 13CO2 enrichment of exhaled air. Results were expressed as percentage of 13C dose excretion per hour and percentage of cumulative 13C after 4h. gastric emptying coefficient (GEC), and gastric half-emptying time (t1/2b). The values for percent of cumulative 13C after 4 h ranged from 30.7 to 52.6% (mean, 40.2%), GEC ranged from 2.7 to 3.4 (mean, 3.0), and the values for t1/2b ranged from 17 to 100 min (mean, 57 min). We conclude that the 13C-octanoic acid breath test can be adapted to preterm infants to allow the study of GE in various conditions.