The present study was undertaken to investigate effects of ethanol extracts of acorn (QAEE) on arterial blood Pressure and respiration, to find out the mechanism of depressor activity of QAEE,. add to determine lethal dosages of QAEE in rabbits and dogs. The results obtained were as follows: 1) After administration of 20 mg/Kg, 30 mg/kg, and 40 mg/kg of QAEE into rabbits the maximum depressor responses observed were respectively 16.3±1.4 mmHg, 28.7±2.0 mmHg and 45.6±3.1 mmHg, while mean depressor responses following administration of 40mg/kg, 60mg/kg and 80mg/kg of QAEE into dogs were 32.2±1.6 mmHg, 39.5±1.5 mmHg, and 47.0±1.6 mmHg respectively 2) Genenally depressor responses increased in proportion to dosage of QAEE administered whereas at same dosage of QAEE depressor responses were greater in rabbit than in dog. 3) It is suggested that depressor activity of QAEE resides mostly in its activity to activate vagus nerves and partly in Its activity to block beta-rceptors. 4) The lethal dosages of QAEE were 50 mg/kg to 60mg/kg for rabbi hue 90mg/kg to 100 mg/kg for dogs. 5) After QAEE administration respiratory rates were generally increased in the rabbit and the dog.