The free-radical copolymerization of ethene and butyl acrylate was studied between 130 and 225 degrees C at pressures from 1500 to 2500 bar. The reactions which were induced either thermally or laser-photochemically were run in two types of continuously operated devices. Reactivity ratio data referring to ethene-rich monomer mixtures are presented. These data allow to estimate the copolymer composition in ethene/butyl acrylate copolymerizations carried out in a wide range of temperatures and pressures.