This publication in the series "Revue de géographie alpine/journal of alpine research" is devoted to the subject of the air in the Alps. The mountain air has played a major role in the history of the Alps since the end of the 18th century. The book, which is in English and French, comprises six scientific articles on the medical, meteorological and tourism aspects of the mountain air. One of the authors also considers the architectural impacts of "healthy mountain air" in an analysis of the design of Swiss sanatoriums built between 1880 and 1914. In total, the book addresses the historical debate on the role of the mountain air in the Alps but without neglecting the present and the future.