Twenty—two forest stands of the Catskill Mountains, New York, in which spruce (Picea rubens), balsam (Abies balsamea), or both were present in the tree canopy, were sampled by means of the quarter method. A matrix of index of similarity values was calculated on the basis of the relative frequency, density, and dominance (importance value) of the mature trees plus the relative density of the saplings. From the matrix a two—dimensional ordination was constructed. The stands were distributed on the first order primarily on the basis of the proportions of balsam and spruce, on the second order primarily on the proportions of hardwoods to spruce and balsam. An ordination based on ten selected species of understory plants was significantly correlated with the first order. The spruce—fir forest of the Catskills is compared with that of the northern and southern Appalachian Mountains as reported in other studies. Although certain northern species present in the Catskills are absent from the southern Appalachians and some species endemic to the southern Appalachians. Spruce is completely absent from several peaks of the Catskill Mountains; no stand was found in which balsam was completely absent. An explanation is advanced based on the ecological behavior of spruce and fir.