High-spin states in Os-173 have been studied by gamma-gamma-coincidence measurements following the Nd146(S-32, 5n) Os-173 reaction. Additional information has also been extracted from the reaction Sm-144(S-32, 2pn) Os-173. Four main sequencies have been identifie as the two signature branches of the bands built on the 5/2+ and 5/2- Nilsson states. The band features have been analysed within the framework of the cranked shell model. The positive-parity band provides evidence for a v(i13/2)2 crossing at low frequency and a pi(h11/2)2 and/or pi(h9/2)2 crossing at higher frequency. In the negative-parity band the upbend starts at relatively low frequency indicating, presumably, an early v(i13/2)2 alignment. There is evidence for another two band crossings possibly due to v(i13/2)2 alignment of a different configuration and a high frequency proton alignment as in the positive-parity band. B(M1)/B(E2) ratios have also been extracted in both bands to deduce further information on the detailed structure of the bands.