3-Thiolpicolinic acid is prepared by reacting a 3-halopyridine, having a 2-substituent which is hydrolyzable to a carboxy group, with an alkali metal salt of p-methoxybenzyl mercaptan, hydrolyzing the 2-substituent to a carboxy group and then cleaving the p-methoxybenzyl group under non-reductive acid conditions. The 3-(p-methoxybenzylthio)pyridines substituted in the 2-position by a carboxy group or a group which is hydrolyzable to a carboxy group are new intermediates.