Using highly potent immune sheep sera, it was possible to demonstrate that: (1) Two rhabdoviruses, classified in the Vesiculovirus genus on morphological grounds but previously considered unrelated, viz., the vesicular stomatitis virus type Indiana (VSV), and Chandipura virus (ChV), show a low-level, but distinct cross-neutralization. This was, in most combinations, considerably increased by complement. (2) The species of cells used for growing the viruses for immunization and for neutralization tests, influenced the level of cross-neutralization. (3) No cross-reaction between VSV and ChV could be detected in the immunodiffusion reaction. (4) Immune sera, raised in sheep by immunization with the two purified rhabdoviruses contained complement-dependent cytotoxic antibodies specifically reacting with the cell species used for growing the viruses.