  We compute the hadron mass spectrum, the quark masses and the meson decay
constants in quenched lattice QCD with non-perturbatively $O(a)$ improved
Wilson fermions. The calculations are done for two values of the coupling
constant, $\beta = 6.0$ and 6.2, and the results are compared with the
predictions of ordinary Wilson fermions. We find that the improved action
reduces lattice artifacts as expected.
