Aim: This was to find out connection between mode of delivery and amounts of Streptococcus mutans (SM) in oral cavity of newborns. Methods: A total of 49 newborns (26 boys and 23 girls) were randomly enrolled in this study. 29 newborns were delivered vaginally (group A) and 20 with Caesarean section (group B). For all enrolled children the mode of delivery as well as the birth weight was noted. At the age of 2 days, the amounts of SM in saliva were investigated in all newborns (Strep Mutans test, Orion Diagnostica). Samples of saliva were collected with microbrushes from tongue and upper and lower alveolar mucosa, incubated 48 hours in a temperature of 37°C. The birthweight and amount of SM in newborns of group A and B were compared. For statistical analysis were used standard methods - the T-test and chi-square test. Results: SM was detected in saliva obtained from tongue in 35 newborns (71 %) and from alveolar mucosa in 39 newborns (79 %). Significant statistical differences were not observed between group A and B including birthweight and amounts of SM in saliva. Conclusion: Early childhood caries could be influenced by many factors including maternal oral health, oral hygiene, nutrition and early transmission of SM from mother to infant. Our preliminary results do not confirm any relation between mode of delivery, birth weight and early SM colonization in newborn's oral cavity. Supported by a grant from the IGA Health Ministry of Czech Republic NS9732-4 Keywords: streptococcus mutans, newborn, mode of delivery