The influence of fire on the regeneration ecology of northern red oak (Quercus rubra L.) and sympatric tree species was examined in mesic hardwood stands in southwestern Wisconsin. A plot in each of four openings was burned in the spring of 1989 and 1990. Density and height growth of tree regeneration, and leaf area index and percent cover of all plant growth forms were monitored on burned and nonburned plots in both years. Tree height growth was also measured in 1991. Fire substantially decreased tree regeneration density, and grasses and sedges became the most abundant vegetation on burn plots. Post-fire survival varied among the most common tree species. Densities of Acer saccharum Marsh. and Ostrya virginiana (Mill.) K. Koch decreased by more than 80%, while those of Q. rubra and Carya cordiformis (Wangenh.) K. Koch increased or were unaffected. Net 2-year height growth decreased by 65% or more on burn plots for all of the common tree species except Q. rubra and C. cordiformis, which experienced losses of 25-35%. The differential effects of fire on species survival and growth enhanced the competitive status of Q. rubra. In the absence of fire, it was uncertain whether Q. rubra would maintain a dominant or codominant position in the canopy of these developing stands.