Novel benzimidazole derivatives of the formula: ##STR1## wherein R.sup.1 is a lower alkyl group, a lower alkenyl group or a lower alkynyl group, R.sup.2 is hydrogen atom, a lower alkyl group or a lower hydroxyalkyl group, and n is 2 or 3, or a pharmaceutically acceptable acid addition salt thereof, which have potent antihistaminic activity with less toxicity and hence are useful as an antihistaminics, and a process for the preparation of the compounds, and a pharmaceutical composition useful as antihistaminics containing the compound as an essential active ingredient.