Background. Clostridium difficile has long been considered to be a nosocomial pathogen but has emerged in the community in recent years. During infancy, asymptomatic C. difficile colonization is common. However, knowledge of colonization determinants and strain characteristics is limited. We studied the dynamics of C. difficile colonization in healthy infants from the community. Determinants of colonization and strain genotypes were also determined in a cohort of infants attending day nurseries. Methods. A 1-year follow-up study involving 10 healthy infants was performed to determine the incidence and kinetics of intestinal C. difficile colonization. In addition, a 1-point study involving 85 healthy infants (age, 0-3 years) from 2 day nurseries was performed. C. difficile isolates were typed by polymerase chain reaction-ribotyping and analyzed for the presence of toxin genes. Results. During the follow-up study, all infants acquired C. difficile and were colonized for several months. An early (neonatal) and a late (4-6 months of age) acquisition period were identified. In day nurseries, 38 infants (45%) carried C. difficile, with 11 (13%) carrying a toxigenic isolate. Age and several environmental factors were associated with the C. difficile carrier state. Strains causing disease in adults were identified in infants. Interestingly, no infant carried the common epidemic 027 or 078 strains. Conclusions. This study provides information on the dynamics of colonization in infants in the community and on the genotype of involved strains. C. difficile colonization appears mainly as an age-dependent process. Pathogenic strains circulate in asymptomatic infants from the community, who represent a potential reservoir of pathogenic strains.