Gap junction channels which are responsible for direct intercellular communication are composed of connexin proteins. Different connexins are distributed in a tissue-specific manner. Up to now only connexin26 has been identified to be widely expressed in the inner ear. In order to investigate the role of additional gap junction proteins, the expression of connexin30 and 43 was investigated in the rat cochlea. Connexin26 and connexin30 were both expressed in the spiral limbus, the spiral ligament, the stria vascularis and between supporting cells of the organ of Corti. Double-labeling experiments suggest that both connexins are partly colocalized between cells. Weak staining of connexin43 could only be detected in the stria vascularis, the spiral ligament and between organ of Corti supporting cells. The corresponding transcripts for connexin26, 30 and 43 could be detected by Northern blot analysis. The expression of different gap junction channels in the cochlea suggests functional diversity. Gap junctions in the inner ear may control ion concentrations of cochlear fluids or act as conduits through which glucose and other metabolites diffuse.