Résumé : The synthesis of diorganotin(IV) derivatives of thiosalicylic acid, of 3‐aza‐2‐thiosalicylic acid, and of several related compounds is reported. Their characterization by 1H, 13C, and 119Sn NMR, Mössbauer, and mass spectrometry is described. The in vitro antitumor activity of selected derivatives against two human tumoral cell lines is discussed. Copyright © 1991 VCH Publishers, Inc.