We describe the pathologic and immunohistochemical findings in five cases of rabies in the insectivorous Pallas's mastiff bat (Molossus molossus) in the city of Patos, state of Paraíba, northeastern Brazil. All cases were found during the day, in different neighborhoods, prostrate and unable to fly. No significant lesions were observed at necropsy or on histologic examination. The brains of the five bats showed strong immunohistochemical labeling for rabies virus in the form of large corpuscles or multiple clusters of granules within the perikarya of neurons in different areas of the brain, mainly in the cerebral cortex and cerebellar Purkinje cells. Three bats tested by direct immunofluorescence and mouse inoculation were also positive for rabies. These data demonstrate that M. molossus may be infected with the rabies virus and develop rabies, even without histologic lesions in the central nervous system, and can be a source of infection for humans and domestic animals.