The plant Kielmeyera rugosa Choisy (family Calophyllaceae), popularly known as 'pau-santo', is traditionally used in Brazilian folk medicine. Recently, the dichloromethane extract-dichloromethane partition from stems of K. rugosa (KR) has shown positive results in our cytotoxic screening programme. Therefore, the aim of this study was to validate the antitumour activity of KR on sarcoma 180 tumour-bearing mice. KR showed antitumour activity with both administration routes: intraperitoneal (50 and 100 mg/kg/day) and oral (100 and 200 mg/kg/day). Tumour growth inhibition rates were 40.8-34.9% and 25.4-51.8% after intraperitoneal and oral administrations, respectively. Treatment with KR did not significantly affect body mass, macroscopy of the organs or blood leukocyte counts. In conclusion, KR exhibited an in vivo antitumour effect without substantial toxicity.