The catalytic behaviour of the superbases Na/NaOH/gamma-Al2O3 and CsxO/gamma-Al2O3 as well as of the basic zeolites Na/NaX and CsxO/CsX were investigated in the Michael addition of ethyl acrylate and acetone. The reactions were carried out in the liquid phase at catalyst loadings varying from 0.05 to 0.1 mol ester/g catalyst.