5-HT(6) receptor-like immunoreactivity has been previously found in association with both neuronal dendrites and cilia in the striatum, nucleus accumbens, olfactory tubercle and islands of Calleja of the rat brain. Using immunogold pre-embedding immunocytochemical techniques to investigate the subcellular localization of 5-HT(6) receptor-like immunoreactivity in cilia, we showed that immunogold particles were associated with their plasma membrane, and not with microtubules. This membrane localization is consistent with a possible physiological role, which is still unknown, of these receptors.