The vegetation of dolomitic outcrops was sampled in a maple forest of southern Quebec. Multivariate analyses have demonstrated the influence of rockiness and size of outcrop on the distribution of herbaceous and woody plants. These results allow the description of five microcommunities. The flora of small cracks and hollows is exclusively herbaceous and of low diversity. Deeper soils support tree seedlings and saplings (mostlyAcer saccharum) and also a diversified herbaceous stratum. The chemistry and mictotopography of outcrops produce mesic soils, rich in organic matter and nutrients. Soil depth segregates among plant species according to the size of their roots. Big outcrops have a more favorable microclimate. Dolomitic outcrops found in maple forests are biogeochemically rich microhabitats, which may support a more varied and abundant vegetation than does the surrounding forest floor. Primary succession on these outcrops is briefly discussed.