Because of the growing importance of the Retinoid X Receptors (RXR alpha, beta and gamma) in the retinoid acid signalling pathway, we have prepared polyclonal and monoclonal antibodies directed against these proteins. For this purpose, either the whole mouse RXR alpha protein expressed in E.Coli, or synthetic peptides corresponding to amino acid sequences common to all RXRs or unique to RXR alpha, beta or gamma, were used as antigens. Antibodies recognizing either all three RXR types (alpha, beta and gamma) or specific for each RXR type were obtained. The antibodies were characterized by immunocytochemistry, immunoblotting, immunoprecipitation and electromobility shift assay (EMSA). These antibodies allowed us to detect the presence of RXR alpha proteins in mouse embryos and in mouse embryonal carcinoma cells (F9 and P19 cell lines) by immunoblotting, immunoprecipitation and EMSA whereas RXR beta could be detected only by EMSA and RXR gamma could not be detected by any of these techniques.