For the first time in Mexico, two cases of acute pulmonary edema of high altitude are reported in a 6 year -old child and in a 16 year- old adolescent; both children lived in the city of Mexico. In identical circumstances, both developed progressive acute respiratory insufficiency on their return to Mexico City after several days at sea level. The final diagnosis was acute pulmonary edema of high altitude. In this paper, the producing mechanisms of this complication are discussed, together with the importance of making it known, in order to put on the lookout the medical personel, who work in the plateau, so that they may be conscious that this disturbance may occur at altitudes like that of Mexico City, (2480 meters above sea level) which is much lower than the altitude considered dangerous. (3000 meters). The most important facts of the clinical picture, together with the treatment recommended are pointed out.