This book is the first comprehensive diatom analysis of the Andes from Venezuela to Patagonia / Tierra del Fuego. Almost everywhere, even in supposed isolated areas and extreme altitudes, cosmopolitan diatoms have been found, which are also typical for Europe resp. the Holarctic. Remarkably some of the well known cosmopolitan diatoms from the Holarctic have not been found in the Andes. There are however a number cosmopolitan diatoms from the southern hemisphere resp. the Andes, which are lacking in Europe. This seems to be one of the main differences between the Andean and European species - associations. Another difference is the disovery of new species all over the Andes. The diatom associations in the Andes differ not only regionally very much, but even quite often locally. This volumes illustrates 3040 taxa for the Andes on photographic plates. 84 taxa have been described as new, some of them bound to altitudes above 3600 m only. 56 other found taxa seem to be new to science, too.