Résumé : The in vitro antiproliferative effects, the toxicity profiles in vivo in mice and the antitumour activity in tumour-bearing mice were screened for five recently synthesized organotin compounds: triphenyltin 5-sulfosalicylate (1), triphenyltin 5-aminosalicylate (2), triphenyltin 4-fluorobenzoate (3), tri-n-butyltin 2,6-difluorobenzoate (4) and di-n-butyltin bis (2,5-dihydroxybenzoate) (5). The in vitro chemosensitivity tests showed that compound 1 has the lowest antiproliferative effect in C26-10. In WiDr, compounds 1 and 5 were less active than the other compounds tested. The IC50 for cisplatin in C26-10 was in the same range as for 1. For compound 3 a steep dose response curve in C26-10 turned out to be remarkably different from the curves of the other compounds. In vivo, compound 1 was most toxic, mainly through paralysis. At their maximum tolerated dose (MTD) for single administration compounds 1, 2, 3 and 4 are inactive against murine colon carcinoma Colon 26. At a single administration, compound 5 was the most active compound with Test/Control ratio (T/C) below 0.6 and Growth Delay Factor (GDF) above 1.0, their respective cut-off levels for sensitivity.