A search for a heavy gauge boson W′ has been conducted by the CMS experiment at the LHC in the decay channel with an electron and large transverse energy imbalance ETmiss, using proton–proton collision data corresponding to an integrated luminosity of 36 pb−1. No excess above standard model expectations is seen in the transverse mass distribution of the electron-ETmiss system. Assuming standard-model-like couplings and decay branching fractions, a W′ boson with a mass less than 1.36 TeV/c2 is excluded at 95% confidence level.