A comparative study is presented of the room‐temperature decay of laser excited microwave photoconductivity and of cathodoluminescence of high quality GaAs multiple quantum wells grown by molecular beam expitaxy and of high quality GaAs liquid phase epitaxial layers. The results from both experiments are inquantitativeagreement and prove that carrier recombination in multiple quantum wells occurs via excitonic decay channels at excess carrier densities less than 1017cm−3. In contrast, band‐band recombination prevails in three‐dimensional material.