This paper assembles a new dataset on corporate income tax regimes in 50 emerging and developing economies over 1996-2007 and analyzes their impact on corporate tax revenues and domestic and foreign investment. It computes effective tax rates to take account of complicated special regimes, such as partial tax holidays, temporarily reduced rates and increased investment allowances. There is evidence of a partial race to the bottom: countries have been under pressure to lower tax rates in order to lure and boost investment. In the case of standard tax systems (i.e. tax rules applying under norma