Cosmological parameters, Omega(M) & &UOMEGA;(Lambda): evidence for accelerating universe

Observational cosmology is currently experiencing a revolution. Resent meas urements of mangitudes vs redshift of very distant type Ia supernovae indic ate that the rate of expansion of the universe is increasing. This accelera tion requires the existence of an energy form that overcomes the gravitatio nal self-attraction of matter, such as the vacuum energy density associated with the cosmological constant (Lambda). I describe how cosmological param eters can be extracted from the measurements of high-redshift supernovae an d discuss the resent results from the Supernova Cosmology Project. I also briefly review alternative techniques to measure cosmological parame ters: CMB anisotropies, cluster of galaxies and lensing statistics of QSOs.