2-[(Phenylthio)methyl]pyridine derivatives inhibited the dermal reverse passive Arthus reaction (RPAR) in the rat. In the same model, indomethacin was inactive, and hydrocortisone was active. Compounds Ia-d also significantly reduced exudate volume and white blood cell accumulation in the pleural RPAR. This pattern of activity was similar to that of hydrocortisone and different from that of indomethacin.