PURPOSE: To inhibit the polymn. during the distillation of (meth)acrylic acid, monomeric methyl acrylates or the like by conducting the distillation in the presence of a phenolic inhibitor and a specified assistant inhibitor which is a soluble manganese or cerium alkanoate of a specified monocarboxylic acid.

CONSTITUTION: A product or a product mixture comprising acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate or a mixture of them is distilled in the presence of 5 to 5,000 ppm, pref. 25 to 500 ppm, of a phenolic inhibitor (e.g. hydroquinone, catechol or guaiacol) and 1 to 5000 ppm (in terms of metal), pref. 1 to 30 ppm, of an assistant inhibitor which is a soluble manganese or cerium alkanoate of a saturated 5-19C monocarboxylic acid.