The physiological and medical literature on the description of acute mountain sickness by Father Acosta in the Peruvian Andes shows many historical misconceptions and clinical misinterpretations. A recent paper by Gilbert (1983) not only contains these traditional misinterpretations but also adds geographical errors in the descrition of the area where Acosta described his sufferings. In view of these facts the authors have made a review of the old and modern writings on the so called Pariacaca story and during an on-site visit to the area of Pariacaca have taken actual measurements of distances, altitudes and geographical locations which they hope will put this story in the context of historial and scientific objectivity. © 1985.