Ethnomedical survey has shown that the seeds of Barringtonia racemosa Roxb are traditionally used in certain remote villages of Kerala (India) to treat cancer like diseases. So the seed extracts were tested for their antitumour activity and toxicity. Intraperitoneal (i.p.) daily administration of 50% methanol extract of this seed to mice challenged with 1 million Dalton's Lymphoma Ascitic (DLA) cells resulted in remarkable dose dependent anti-DLA activity in mice. The optimum dose was found to be 6 mg/kg. This dose protected all the animals challenged with the tumour cells. The efficacy of the drug was found to be better than that of a standard drug, vincristine in this tumour model. However, the oral administration showed only marginal activity compared to i.p. administration. The extract was found to be devoid of conspicuous acute and short-term toxicity to mice, when administered daily, (i.p.) for 14 days up to a dose of 12 mg/kg (which was double the concentration of optimum therapeutic dose). The treated mice showed conspicuous toxic symptoms only at 24 mg/kg. The LD(50) to male mice for a single i.p. dose was found to be 36 mg/kg. The seed extract is an attractive material for further studies leading to drug development.