Thomas Holmes Ravenhill (1881-1952) was an important pioneer in high-altitude medicine but almost nothing has been published about him. He wrote a landmark paper in 1913 that included the classification of high-altitude sickness that is still in use, and it also contained the first accurate descriptions of high-altitude pulmonary edema and high-altitude cerebral edema, although he used different terms. The work was done while he was medical officer at the Collahuasi and Poderosa mines in northern Chile at altitudes he gave as 4,690-4,940 m. Remarkably, the paper was then forgotten until it was rediscovered over 50 yr later, but it is now cited in any comprehensive study of high-altitude illness. Ravenhill graduated in medicine from the University of Birmingham, Birmingham, UK, in 1905 and 4 yr later went to the mines where he spent 2 yr. Subsequently, he served in the Royal Army Medical Corps in the 1914-1918 war and was awarded the Military Cross. He returned to general practice but after a few years gave up medicine altogether. He then made important contributions to archeology and spent the last third of his life in London as a painter, mainly in watercolors. It is unclear to what extent his war experiences brought about his dramatic career change.