The synthesis and spectral characterization of six novel triphenyltin compounds are described. The in vitro antitumour activity of three of these compounds against two human tumour cell lines, MCF-7, a mammary tumour, and WiDr, a colon carcinoma, was determined. All three compounds are more active than cis-platin, etoposide and doxorubicin against both tumour cell lines. They are as active as mitomycin C against WiDr, but less active against MCF-7.