The purpose of this study was to compare the delayed response to Bacillus Calmette-Guérin (BCG) immunization in preterm infants 31.4 to 34.6 weeks of age with full-terms infants by tuberculin test (tuberculin skin test with purified protein derivative [PPD]). One hundred newborns were studied from November 2000 to April 2002, consecutively allocated by convenience in two groups. Group I (GI) included 50 preterm infants from 30 to 34.2 weeks of age at inclusion and 31.4 to 34.6 weeks of age at vaccination. Group II (GII) included 50 full-term newborns. Sick or malnourished patients and those with severe malformations were not included. Newborns were evaluated at 4, 8, and 12 weeks after BCG application for scar measurement. Sixteen weeks after BCG, the PPD with Tubersol was performed. It was defined as a positive reaction when the scar diameter was of 5 mm or more; the same criterion was used for PPD response. Forty-two patients from each group concluded the study. The percentage of positive scar (GI, 64%; GII, 80%; P = 0.142) and the mean of scar diameter (4.5 and 5 mm, respectively) were not statistically significantly different. The rate of positive PPD in GI (81%) and GII (86%), and the mean of PPD in GI (6.7 mm) and GII (6.8 mm) were not statistically different ( P = 0.74). Complications were not observed. This trial showed similar response to PPD after BCG vaccination in preterm and full-term infants.