In my book Introduction to High Altitude Entomology, published in 1962, I summa- rized the results of eight years' studies, mainly on the Himalaya. I have since then had the opportunity of studying the collections of high altitude insects from the Alps, Carpathians, Caucasus, Urals, Alai-Pamirs, Tien Shan, Altai and other im- portant mountains of the world in different museums and institutions in Europe. Through the courtesy and generosity of the Academy of Sciences of the Union of Soviet Socialist Republics, I was also able to personally collect insects and make valuable field observations on the Caucasus, the Alai-Pamirs, Ala-Tau and the Tien Shan mountains. Through comparative studies I have tried to synthesize the fundamental principles of high altitude entomology. I have described here the distinctive characters of the high altitude environment, the ecological specializations of the high altitude insects, their ecological inter- relations and the outstanding peculiarities of their biogeography. I have also pre- sented here an outline of the high altitude entomology of the principal mountains of the world, with brief accounts of their orogeny, geology and vegetation. This book differs from all other contributions in the field in its comparative ecological approach and in the fact that the main emphasis is throughout on the evolution of the high altitude ecosystem as an integral part of the orogeny. High mountains are, in all parts of the world, important and independent centres of origin and differ- entiation of distinctive and highly specialized ecosystems and faunas.