Acute mountain sickness is a pathologic reaction as a result of bad adaptation to high altitudes (greater than 2.500 meters). The main symptoms are headache, nausea, vomits, and insomnia. When severe it can produce oliguria, retinal hemorrhage, ataxia and sometimes coma. Its etiology is not well known. It is considered that the first producer factor of the disease is tissular hypoxia secondary to low partial oxygen pressure existing in areas of high sea level. The treatment consists of descent and the use of dexametasone and acetazolamide.