Monoclonal antibodies specific for cell surface antigens on embryonic chick ciliary ganglion neurons (CG) have been obtained at high frequencies by fractionating spleen cells from immunized mice according to their adhesiveness for cell surfaces of the cultured neurons. Spleen cells from mice that had been immunized with live or lightly fixed (0.125% glutaraldehyde) CG neurons were selected for subsequent hybridization with myeloma cells after fractionation on lawns of CG neurons in tissue culture. Immunized spleen cells were cultured with the neurons for 4-7 days prior to fractionation. Three groups of spleen cells were selected for fusion with a myeloma cell line: a non-adherent population of spleen cells, a population of spleen cells that could be removed from the neuronal cells by shaking on a vibratory shaker for 1 h, and a population that could be removed from the neuronal cells only by treatment with low concentrations of trypsin. Of the 3 groups of spleen cells, the population that required trypsin treatment produced the greatest number of hybridomas specific for neurons and for neuronal cell surfaces. Fewer neuron-specific hybridomas resulted from fusion of the group of spleen cells that could be removed from the antigen lawn by shaking. None of these was specific for the CG neurons. No neuron-specific hybridomas resulted from the fusion of the cells that did not adhere to the neuronal cells, and at most only 1 neuron-specific hybridoma resulted from fusions of comparable groups of unselected spleen cells (spleen cells from immunized animals which were not selected on antigen lawns).