SYNOPSIS. A new large trypanosome was found in the blood of 19 Artibeus lituratus and 2 Phyllostomus hastatus bats. The monomorphic trypanosome resembles Trypanosoma megadermae in some respects, but differs from it in that it is larger and has a short flagellum, both extremities are very tapered, the kinetoplast is very close to a small nucleus and there is a greater distance between the kinetoplast and the posterior extremity of the body. In diphasic blood‐agar cultures there is a great variety of odd multiplication forms not described from other trypanosome cultures, but some simulate T. cruzi . This trypanosome is not capable of infecting mice, tissue culture cells, Carollia perspicillata bats, or triatomids, but is able to infect A. lituratus bats. Culture forms of the trypanosome inoculated intra‐coelomically are pathogenic for several species of triatomids, and multiply in the hemolymph of Rhodnius prolizus , often producing forms similar to crithidiae of T. rangeli . Culture forms of the trypanosome seem to have common antigens with T. cruzi . This new species is described as Trypanosoma pifanoi .