The effects of ethanol on the toxicity of 2, 4-Dichlorophenoxyacetic acid in ICR mice were examined. The results were summerized as follows; 1. The LD$sub$50/ of 2.4-dichlorphenoxyacetic acid sodium injected intraperitoneally in mice was approximately 367 mg/kg. When the animals were administered with ethanol, 2 ml/kg or 4 ml/kg the LD$sub$50/ of 2.4-D sodium were decreased to 338 mg/kg or 32 mg/kg, respectively. 2. In the acute experimental group, spontaneous motor activity in the ANIMEX system exhibited dose-dependent decrease in mice administered with 2.4-D sodium and ethanol. 3. However, in subacute experimental group, spontaneous motor activity in the ANIMEX system exhibited dose-dependent increase in mice treated with ethanol.