Résumé : The synthesis of dimethyl‐, diethyl‐ and/or di‐t‐butyl‐tin(IV) derivatives of substituted salicylic acids of the type a, (X‐Y‐2‐OH‐C6H2COO)2SnR2 (X, Y  H, H; H, 5‐CH3; H, 5‐Cl; H, 5‐F; H, 3‐CH3O; H, 5‐CH3O; 3‐CH3, 6‐(CH3)2CH; 3,5‐[(CH3)2CH]2 and 4,5‐benzo) and b {[R2(X‐Y‐2‐OH‐C6H2COO)Sn]2O}2 (X, Y  H, 3‐CH3O; H, 5‐CH3O: 3‐CH3, 6‐(CH3)2CH; 3,5‐[(CH3)2CH]2 and 4,5‐benzo) 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, MCF‐7 and WiDr, is presented. Copyright © 1991 John Wiley & Sons, Ltd.