Determination of median lethal dose (LD50) is one way to measure the potential short-term toxicity (acute toxicity) of a substance to a biological system that sufficient to kill 50 percent of a population of tested animals. Acute toxicology studies in vivo are essential to drug development experiments that estimate the LD50 in rodents. Toxicity tests are usually performed by pharmaceutical manufactures in the investigation of a new drug. Medemia argun fruits have been found in the tombs of ancient Egypt including celebrated tomb of Tut Ankh Ammon. Nowadays, little detailed phytochemical and pharmaceutical studies have been reported for Medemia argun. Scientists exhibited by in vitro experiments that the proanthocyanidin fraction from Medemia argun nuts can be useful as a protecting factor against oxidative/nitrative stress associated with different diseases such as cancer, cardiovascular and neurodegenerative diseases. In this study, we determined the LD50 of the Medemia argun seed's crude ethanolic extract in vivo using the experimental mice' model to open the field for further scientific researches. Several doses of Medemia argun ethanolic extract was used in LD50 experiment that carried out on male albino mice administered intraperitoneally for 14 days. The results showed that the LD50 of the ethanolic Medemia argun crud extract was (200 mg/kg) where half of the tested animals in such group were dead, our data substantiate an evidence that Medemia argun seed's extract could be safe up to (150 mg/kg) that there was no mortality was reported and may be effective at dose (100 mg/ kg).