An open hose clamp with a tightening mechanism in the form of a so-called Oetiker ear. The tightened condition is locked by toothed portions which mutually engage outside the area of the ear on the side of the ear remote from the outer clamping band end. In the locked tightened condition, the ear is free of forces so that the hose clamp retains its clamping function even if the outward projecting ear is damaged.