The anti-inflammatory activities of dichloromethane, ethanol, and boiling water extracts of the brown seaweeds Undaria pinnatifida (Harvey) Suringar and Laminaria japonica Areschoug were examined. Ethanol extracts (0.4 mg/ear) of U. pinnatifida inhibited inflammatory symptoms in mouse ear edema by 95.3%, and dichloromethane extract inhibited erythema by 65.5%. Dichloromethane and ethanol extracts (4 g/kg bw) of L. japonica demonstrated potent antipyretic activity. Activities of the seaweed extracts were similar to those of the commonly used drugs indomethacin and acetyl salicylic acid. No acute toxicity was observed after p.o. administration of each extract (5 g/kg bw). These results were in agreement with the claims of the health care industry and indigenous medicine that the above seaweeds can be used as an effective remedy for inflammation-related symptoms.