Physics with CMS in the first year of running

The CMS detector is one of the two general purpose experiments that will study the collisions produced by the Large Hadron Collider (LHC). The LHC is supposed to start its operation in 2007 at an instantaneous luminosity of 2x10^33 cm-2 s-1. This may well result in an integrated luminosity of 10 fb-1 after the first year of running. The physics reach of CMS with such an amount of delivered luminosity is presented for some of the most important fields of study: Standard Model physics, Standard Model and Minimal Supersymmetric Standar d Model Higgs searches.