The plant Crataegus monogyna has action against cardiac insufficiency, angina and arrhythmia. The anti-inflammatory properties of the cycloartenol fraction from this plant have been investigated. Chromatographic fractionation of the hexane extract of Crataegus monogyna Jacq. (Rosaceae) furnished a triterpene fraction containing cycloartenol as the main component (80.87%). The anti-inflammatory activity of the fraction was tested against hind-paw oedema induced by carrageenan in rats. At the highest oral dose (40 mg kg-1) inhibition was 61.5 and 52.5% at 3 and 5 h respectively. In the mouse carrageenan peritonitis test, the triterpene fraction given orally inhibited peritoneal leucocyte infiltration (41.9, 64.7 and 89.4% at 10, 20 and 40 mg kg-1, respectively). The fraction also showed weak inhibition of phospholipase A2 (PLA2) in-vitro. These results suggest that the fraction containing cycloartenol as the main component exerts an important anti-inflammatory action in-vivo by reducing the oedema.