Monoclonal antibodies were developed against cerebral ganglia (CG) of the mussel Mytilus edulis by the immunization of mice with unpurified homogenates of these organs. The screening protocol of hybridoma was based upon immunohistological observations of cytocentrifugated ganglia cells. A panel of 29 monoclonal antibodies (MABs) specific of CG epitopes was harvested and subsequently used for the immunocytochemical study of CG cells. Several subpopulations of ganglia cells were specifically revealed by MABs. Identification of epitopes involved in growth control was approached via the application of a bioassay allowing the assessment of protein synthesis stimulation. MAB 42 and 46 affected amino acid incorporation induced by CG extract. These results lead to the conclusion that the epitopes recognised by these antibodies are involved in growth control. An immunoenzymatic assay was performed with CG extracts for quantitative analyses of epitopes. © 1994.