Abstract: Sixteen antitumour agents including Thio-TEPA, BCM, HN₂, MBAO, TEM, AT-16, AT-222, AT-290, AT-346, AT-581, 3P, Ho-14, Sb-57, Sb-71, AC-808 and Actinomycin K were tested in rabbits bearing Brown-Pearce carcinoma. AT-581(o-bis-(2-chloroethyl)-aminomethyl-phenylalanine dihydrochloride) was found to produce a marked inhibitory action on this tumour.Intravenous injections of 0.7 mg/kg/day for 12 days prolonged significantly the survival time of the rabbits (130% prolongation) and strongly inhibited the metastasis of the tumour in the lungs and the liver. When the dose was raised to 1 mg/kg, a more pronounced effect was observed. Under the same experimental conditions, the remaining 15 compounds exhibited no obvious therapeutic action. The experimental method and the criteria of effectiveness employed in this paper were also discussed.