The present invention provides imidazole derivatives of the formula I ##STR1## wherein Het represents 1H-imidazol-1-yl which is unsubstituted or is substituted by lower alkyl, One of the symbols X and Y represents the epithio radical -S- or the ethenylene group --CH.dbd.CH--, and the other represents the direct bond, and N represents 1 to 4, And the rings A and B, besides being substituted by the radical -C.sub.n H.sub.2n -Het, are not substituted or are further substituted, and the ring C is unsubstituted or substituted, and the monoacid acid addition salts, in particular the pharmaceutically acceptable monoacid acid addition salts thereof. These new substances possess valuable pharmacological properties, in particular antidepressant activity, and can be used for the treatment of mental depressions. Specific embodiments are 1-[(naphtho[1,2-b]thien-4-yl)-methyl]-1H-imidazole and its pharmaceutically acceptable monoacid acid addition salts, and pharmaceutical compositions containing them.
