How do plant species richness and community composition vary during initial postfire succession in relation to fire severity and local environmental conditions? We recorded vascular plant species present within 10-m2 plots at 589 permanent sampling points distributed throughout nine patches of crown fire from the 1988 Yellowstone fires. Plots were sampled in 1991, 1992, 1993, and 1996; and 391 species were documented. Species richness generally increased from 1991 to 1993 but decreased or remained constant from 1993 to 1996. Many species that disappeared were opportunistic annuals (e.g., Collinsia parviflora), but species of mature forest also were lost (e.g., Arnica cordifolia). ANOVA indicated that the best predictors of species richness and compositional change were geographic location, total biotic cover (positively correlated with richness), and total cover of tree seedlings (negative correlation). Ordination revealed that richness and composition differed among fire severity classes through 1993, but plots in all severity classes appeared to be converging by 1996. Plots on infertile substrates were becoming increasingly similar by 1996, but appeared to be diverging from plots located on fertile substrates.