Objectives : This study aimed at evaluation of the effects of Gastrodiae Rhizoma on brain edema and aquaporin water channel expressions in the brain. Methods : Brain edema following intracerebral hemorrhage (ICH) was induced by the stereotaxic intrastriatal injection of bacterial collagenase type VII in Sprague-Dawley rats. Then ethanol extract of Gastrodiae rhizoma was treated once a day for 3 days. Brain edema % and water contents, and cell size of neurons in the cerebral cortex were examined. Immuno-histochemistry was processed for AQP4, AQP1, and AQP9 expressions in the brain sections and area % of immuno-labeling was analyzed with image analysis. Results : 1. Ethanol extract of Gastrodiae Rhizoma reduced brain edema of ICH induced rats significantly. 2. Ethanol extract of Gastrodiae Rhizoma reduced excessive brain tissue water contents of ICH induced rats significantly. 3. Ethanol extract of Gastrodiae Rhizoma reduced cellular edema of neurons in cerebral cortex of ICH induced rats significantly. 4. Ethanol extract of Gastrodiae Rhizoma reduced AQP4 immuno-positive area % in cerebral cortex and external capsule of ICH induced rat brain significantly. 5. Ethanol extract of Gastrodiae Rhizoma reduced AQP9 immuno-positive area % in glia limitans externa of ICH induced rat brain significantly. Conclusions : These results suggest that Gastrodiae Rhizoma reveals protective effects against brain edema and cytotoxic edema of neurons by means of down-regulation of AQP4 expression in the brain.