We assessed the pattern of acquisition and loss of Helicobacter pylori infection in a cohort of 212 children from a biracial community with a homogeneous socioeconomic class. The children were followed over 12 years (1973-1974 to 1985-1986) from childhood to young adulthood. H. pylori status was assessed by the presence of serum IgG antibodies to H. pylori. At ages 7-9, 19% of children had H. pylori infection (40% of blacks vs. 11% of whites; P = .0001); 12 years later, 33% were seropositive. The higher prevalence among blacks remained (P = .0001). During follow-up, 22% of children became infected; the rate of acquisition was fourfold greater among blacks than among whites (P = .001). Over the 12-year period, infection was lost in 50% of whites compared with 4% of blacks who either remained infected or became reinfected. H. pylori infection in childhood is affected by both acquisition and loss of infection in different ethnic groups. This observation is critical for understanding the epidemiology and transmission of H. pylori infection.