A process for dehydrogenating organic compounds, in particular paraffins and naphthenes, is carried out in the presence of a supported catalyst comprising a group VIII metal such as platinum, and tin, at least a portion of which interacts strongly with the group VIII metal in the catalyst in the reduced state. In the partially oxidised state, the catalyst contains at least 10% of tin in the form of a reduced tin species with oxidation state 0, said species having an isomer shift in the range 0.80 to 2.60 mm/s and a quadrupolar splitting in the range 0.65 to 2.00 mm/s.