Reparametrization invariance as gauge symmetry

Reparametrization invariance treated as a gauge symmetry shows some specifi c peculiarities. We study these peculiarities both from a general point of view and by concrete examples. We consider the canonical treatment of repar ametrization-invariant systems in which one fixes the gauge on the classica l level by means of time-dependent gauge conditions. In such an approach on e can interpret different gauges as different reference frames. We discuss the relation between different gauges and the problem of gauge invariance i n this case. Finally, we establish a general structure of reparametrization s and its connection with the zero-Hamiltonian phenomenon.