The aim of the present study was to explore the probable antiinflammatory effect of Hypericum triquetrifolium Turra. in a rat model of carrageenan induced inflammation. Male Wistar rats were treated intraperitoneally with 0.4% dimethlsulphoxide (DMSO) (as control group) and H. triquetrifolium extract (25, 50, 60 mg/kg), 30 min before 0.1 ml 1% carrageenan injection. Paw volume was measured before and 1, 2, 3, 4, 5 and 6 h after the injection of carrageenan. The results are expressed as the mean+/-s.e. mean and the statistical significance of differences between groups was analyzed by One Way Analysis of Variance (ANOVA). The intraplantar injection of carrageenan caused a time-dependent paw edema in the rat although saline injection caused no swelling. Intraperitoneal administration of H. triquetrifolium extract (25, 50, 60 mg/kg) inhibited paw swelling dose-dependently at 2. 3. 4. 5 and 6 h after carrageenan injection (P < 0.05). We can conclude that H. triquetrifolium extract may exert an antinflammatory effect in rats. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.