Oropouche virus (arbovirus family Bunyaviridae, Simbu serological group) was experimentally transmitted from man to hamster by the bite of the midge Culicoides paraensis. Infection rates and transmission rates were determined after the midge had engorged on patients with viremia. The threshold titer necessary to enable infection or transmission by the midges was approximately 5.3 log10 of the median lethal dose of the virus in suckling mice per milliliter of blood. Transmission was achieved 6 to 12 days after C. paraensis had taken the infective blood meal. This represents conclusive evidence of transmission of an arbovirus of public health importance to man by a member of the Ceratopogonidae family.