Assuming the fact that the highest specific secreting hybrids number has been recorded with Iq secreting spleen cells, we did some immunizing protocols to maximize the ELISA reacting antibodies: for this Balb/c mice were primed intra-peritoneally with vaccine containing inactivated rabies (P.V. strain). Half of them were boosted intravenously with the same concentrated purified and live virus. We performed a series of hybridizations, at different times (i.e. 10, 15, 20, 75 days), between the rabies committed splenocytes and the SP 2/0 non secreting myeloma cells. Successful hybrids secreting antibody to rabies virus have only been obtained at the earliest and the latest time of fusion, essentially with the intravenous booster. They were initially screened by ELISA test for PV binding and about 65% of the colonies were generally positive. Clones directed against nucleocapsids were revealed by immunofluorescence of the rabies infected fixed cells, and those directed against glycoprotein by the neutralizing test and rabies infected live cells. From the early fusion we also produced hybrids secreting IgG (60%) or IgM (40%). At that time IgG/IgM distribution of specific hybrids do not correlate to that seen for ELISA reacting antibodies. It suggests that the IgG secreting spleen cells are the preferential fusion partners or the most vigorous ones.