Colostethus marchesianus was described from Missão Taracuá in Amazonas, Brazil, in 1941. Two specimens were collected in 1924 by Douglas Melin, a Swedish naturalist who led an expedition to the site. The name Colostethus marchesianus has since been applied to many populations of frogs in Amazonian Brazil, Colombia, Ecuador, Peru, and Bolivia. The type specimens are in poor condition; in addition, tadpoles, calls, and reproductive data were not obtained at the time of collection of the original specimens. Tadpoles and calls are critical in helping distinguish among morphologically similar species. Differences in morphology and calls from various widespread populations have led us and other workers to conclude that populations currently referred to as C. marchesianus represent a number of similar species. With the objective of obtaining adult frogs for redescription, tadpoles, and calls, two of us visited the type locality in April and May 2000. Only one species of Colostethus was present in the area. We obtained adults and recordings of the call and raised tadpoles (described elsewhere) taken from the backs of parent frogs. Colostethus marchesianus from the type locality differs from specimens from Colombia, Venezuela, Ecuador, and Peru based on a variety of characters described in the literature. Thus, frogs from those localities appear not to be the same species as C. marchesianus. The detailed redescription provided herein should help future workers distinguish populations of similar species from C. marchesianus.