Background/aims: The aim of this prospective study was to determine the seroprevalence rates of Helicobacter pylori in mother and infant pairs and to discuss the possible fecal-oral transmission route of Helicobacter pylori infection in the early years of life. Methods: Forty-eight mother-child pairs were followed for 12 months. Helicobacter pylori IgG and hepatitis A virus (HAV) IgG levels were measured in maternal sera, infant sera and breast-milk samples at birth and in breast-milk samples and infant sera at follow-up visits. Results: At birth, the rate of Helicobacter pylori positivity was 81.25% in breast-milk and 95.8% in maternal and infant sera. Although there was a decrease in seropositivity in both baby sera and breast-milk at the age of nine months, an increase was observed in the 12(th) month. Hepatitis A virus IgG was measured to show whether Helicobacter pylori and hepatitis A virus use the same transmission routes. Hepatitis A was positive in all infants' sera, in 95.8% of mothers' sera, and in 68.75% of breast-milk samples. Seropositivity rates in infants whose mothers were seropositive for Helicobacter pylori and hepatitis A virus decreased gradually. There was an increase after the 9(th) month of life. Conclusions: Helicobacter pylori seroprevalence rates are high in Anatolia. It is possible that the decrease in breastfeeding with increased introduction of supplemental foods may lead to an increased risk of exposure to Helicobacter pylori.