Résumé : Proton and carbon‐13 chemical shifts and coupling constants of 2‐mercapto‐4‐pyridinecarboxylic acid, 4‐mercapto‐2‐pyridinecarboxylic acid and their seven respective methylated derivatives are reported. Substituent effects are discussed. Copyright © 1985 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim