The antitumour activity of diethoxy-(1-phenyl-1,3-butanedionato)titanium (IV) (DBT) in comparison to cis-dichlorodiammine platinum (cisplatin, cis-DDP) and cyclophosphamide (CTX) against human breast, colo-rectal and lung tumour lines growing as xenografts in nude mice was investigated. The antitumour activities and toxicities of DBT and cis-DDP are comparable whereas CTX was the most effective agent.