Chloroform extracts of Bursera fagaroides (Burseracea) have previously shown antitumour activity against the Walker carcinoma 256 tumour system (WA16). In the present work we have determined the cytotoxic and antitumour activity of the ethanol extract (70%) of the bark of B. fagaroides using the L5178Y lymphoma. The cytotoxic activity is expressed as the ED50 of the L5178Y lymphoma cells in culture, (20 µg/mL) whilst the antitumour activity was shown via a tumour growing inhibition test, measuring survival of BALB/c mice (2 × 104 cells L5178Y i.p.). 24 h after inoculation mice were treated with 50 or 100 mg/kg of extract daily, over 15 days in independent groups of 10, using two administration routes. We observed the tumour evolution with and without treatment. Oral administration resulted in 8% of mice being tumour free after 60 day whilst intraperitoneal administration showed 26% survived at a dose of 100 mg/kg/day for 15 days. A significant increase in the survival of the treated animals (at 50 mg/kg/day over 15 days) was found compared with those treated with placebo or without treatment