The invention is directed to a process for the preparation of α,β-unsaturated acids, esters and amides from α- or β-hydroxycarboxylic acids or esters or precursors in high yields and high selectivity. The α,β-unsaturated acids or esters are optionally prepared in the presence of specific dehydration and/or esterification catalysts. The α,β-unsaturated amides or substituted amides are prepared optionally in the presence of a dehydration and/or amidation catalyst. The source of α- or β-hydroxycarboxylic acids or precusor is preferably from a renewable resource. The precursor is defined herein.