[en] In an experiment in the CERN SPS charged hyperon beam, a sample of 16,000 Ω^- decays was collected at an Ω^- momentum of 131 GeV/c. The Ω^- lifetime, the branching ratios and decay asymmetry parameters for the main decay modes were measured, giving: tausub(Ω^-) =(0.823 +- 0.015) x 10^-10s. For the rare decay modes the branching ratios were obtained. A sample of 32,000 Ψ^- decays collected under the same experimental conditions gave a new measurement of the Ψ^- lifetime: tausub(Ψ^-) = (1.652 +- 0.051) X 10^-10s. Combining the measurements of the present experiment with those obtained in a previous experiment in the SPS hyperon beam gives: tausub(Ω^-) = (0.823 +- 0.013) X 10^-10s. The experimental results are compared with theoretical calculations