We conduct a study of the dry forest in areas of scant rainfall in the Dominican Republic; these are sites with particular endemic habitats, as the samples reveal a high rate of local and insular endemic species, with 84 (24.85%) endemisms. This work covers dry forests rich in coarse spiny plants and includes a statistical (multivariate analysis), phytosociological and catenal study of the vegetation. We analyse the floristic composition, ecology, distribution and richness in endemisms of each association. The bioclimatic analysis reveals the different thermotypes and ombrotypes on the island, and locates the proposed plant associations in the infra-and thermotropical thermotypes, and in the arid, semiarid and dry ombrotypes. As a result of this phytosociological analysis, we propose the new alliance Harrio nashii -Acacion skleroxylae and four plant associations: Harrisio nashii -Prosopidetum juliflorae, Crotono poitaei -Erythroxyletum rotundifolii, Lonchocarpo pycnophylliCylindropuntietum caribaeae and Neoabbottio paniculatae -Guaiacetum officinali; these associations connect catenally with the subhumid forest and mangrove swamps.