Decomposition rate of leaves in rivers have been shown to be dependent on physical (temperature and velocity), chemical (nutrients and pH) and biological (macroinvertebrates) variables of the river but also of the morphological and chemical composition of leaves. In this study, we compared the colonization rate of hyphomycetes in eight species of trees generally found along Venezuelan rivers. Colonization rates were similar among species since maximum density of conidia was obtained in leaves with 10 days of incubation after which density abruptly drops (50%) for all species but one (Erythrina poeppigiana). Almost no conidia were present after 23 days of incubation. Similarly, no significant difference (p < 0.001) was obtained between coarse mesh bag (5mm) and fine mesh bag (0.5 mm) , indicating a possible minor role of invertebrate in decomposition, even though their density on coarse-mesh bags was higher than in the river (24 and 4 org/m²) . Density of hyphomycetes varies among leaves species with Mangifera indica having the highest (> 600 conidia/ml) while lower density was in Andira jamaicensis (< 200 conidia/ml). Similarly, no difference in colonization was noted among species since the same hyphomycetes were the most common and abundant (Clavatospora tentacula, Heliscus submersus, and Lunuluspora curvula).