We have investigated the sidewall recombination in dry‐etched GaAs/GaAlAs wires with widths between 12 &mgr;m and 300 nm using picosecond spectroscopy. The wires were fabricated with electron beam lithography and different reactive ion etching processes. The excitonic lifetimes decrease strongly with decreasing wire widths due to sidewall recombination. Using a model calculation to fit the experimentally observed width dependence of the lifetimes the surface recombination velocity is determined to beS=2×106cm/s at 50 K.Sincreases with temperature and is independent of the etching process.