Phenological patterns of dry tropical forests have been related to environmental factors, mainly rainfall and insolation, and to plant endogenous rhythms inherent to trees as large, perennial plants. Superimposed to these environmental ('external hypothesis') and intrinsic ('endogenous hypothesis') explanations, there may be phylogenetic constraints contributing to shape phenology. The phenology of tree and shrub species with fleshy fruits in a Dry Chaco forest in Argentina was studied addressing these hypotheses and following two approaches, with the species average values taken as independent data points, and removing phylogenetic effects. The hypotheses addressed are largely complementary to one another. Strong environmental restrictions conditioned general flowering patterns with specieś endogenous characteristics acting secondarily. Phylogenetic patterns were also masked by climatic variables. When considering fruiting phenology, however, phylogeny, representing a set of specieś shared traits, predominated over environmental restrictions.