Résumé : Proton and carbon‐13 chemical shifts and coupling constants of 2‐mercapto‐3‐pyridinecarboxylic acid, 3‐mercapto‐2‐pyridinecarboxylic acid and their seven respective methylated derivatives are reported. Substituent effects are discussed. Copyright © 1983 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim