A series of tetrahydrobenzindoles was prepared, and the affinity of these compounds for the 5-hydroxytryptamine7 (5-HT7) receptor and other receptors was evaluated. Most of the compounds showed high affinity for the 5-HT7 receptor, and 2a-[4-(tetrahydropyridoindol-2-yl)butyl]tetrahydrobenzindole derivatives (26a-j) exhibited high selectivity for this receptor. The nature of the substituent at the 9-position of the tetrahydropyridindole ring affected the affinity for the 5-HT7 receptor, and the 9-carbamoyl moiety afforded increased selectivity. Compound 26j exhibited high affinity for the 5-HT7 receptor, with at least 280-fold selectivity over the 5-HT2 receptor. In a functional model of 5-HT7 receptor activation, this compound was confirmed to have 5-HT7 receptor antagonist activity. It should be a useful tool for clarifying the biological role of the 5-HT7 receptor.