Seasonal patterns in growth and dynamics of 13 epixylic bryophyte species (six liverworts and seven mosses) were studied within permanent plots in the Ž ofínský prales old-growth forest in south-eastern Bohemia, Czech Republic. Transparencies were used to record positions and cover of bryophyte colonies within each plot twice a year (in spring and autumn) for periods of 1-4 years. Percentage growth of species populations and growth dynamics of their colonies were analysed in order to identify seasonality in their growth. Establishment of bryophyte colonies and their expansion, as well as pair-wise overgrowth of adjacent colonies of different species were compared in order to identify competitive interactions between bryophyte species. Bryophytes grew faster during the winter season (October-April) than during summer, and the various species did not differ in their percentage growth. The growth dynamics of bryophyte colonies was highly seasonal and the species differed in their dynamics pattern. The expansion and retreat (local extinction) of bryophyte species were greatest in winter, and the stability of colonies was, therefore, higher in summer. Interspecific competition among the species studied appears to be low.