Background and Objectives: Considering the BCG vaccination in neonatal period, a prospective study was done with following purposes: Result of PPD test after BCG vaccination in neonatal period, its comparison in breast and non-breast fed infants, evaluation of the size of BCG vaccination scar, if there is any relationship between the size of scar and PPD test and finally observing how many of these infants develop BCG adenites.Materials and Methods: To fullfill the above objectives 150 neonates (87males and 63 females) born in Kermanshah province and who received BCG vaccine by an expert technician after birth, at 3 months of age, were enrolled in the study. PPD test was done by 0.1 ml of 5 units tuberculin solution made by Razi Institute. Results: Of the total neonates studied, 146 infants (97.33%) were found to have BCG scar, the mean size of scar being 5.28±1.56 mm, and there was no significant difference between boys and girls (p>0.05). After 72 hours Mantoux test results showed mean size of 5.1±3.25 mm. In 68 infants (45.33%) the size of scar after Mantoux test was less than 5 mm,70 infants (46.66%) had between 5-9 mm ,11infants (7.33%) had 10-14mm and only one case (0.66%) had 15mm. There was no meaningful difference between males and females (p>0.05).Among those infants who did not had BCG scar, except in one case, others were negative for PPD test, while in infants who had BCG scar but the Mantoux test was negative, the mean size of scar was 4.42±3.72mm. Those infants who had Mantoux test more than 5mm , the mean size of the scar was 5.85±3.3mm.There was a direct relationship between the size of scar and Mantoux test (p<0.05). There was no statistically significant difference regarding the Mantoux test and BCG scar size between breast and non-breast fed infants (p>0.05).Axillary adenites were noticed in 5.33% of the infants.Conclusion: The present study shows that 97% of neonates who are vaccinated after 3 months of birth later develop BCG scar and they have increased immunity against tuberculosis. Secondly, the diagnosis of the tuberculosis on the basis of Mantoux test (more than 10 mm) in vaccinated infants is not absolute and thus, other complementary tests are required.