A diverse Coleoptera fauna of 462 species in 48 families was collected from 41 locations in the Parque Nacional de Puyehue and adjacent parts of the Lake Region of southern Chile. The sample locations ranged from rain-forest habitats at sea level to Andean tundra habitats at 1,500 m above mean sea level (msl). Cluster analysis of a Dice similarity coefficient matrix revealed a broad pattern of bioassociations within the large data base. Evidence from fossils indicates that the lowland beetle fauna during the interval 26,000 to 15,500 Carbon 14 years before present (yr BP) had a low diversity and was dominated by species of open-ground habitats. Forest species appeared in the lowlands between 15,000 and 14,000 yr BP, at about the time of the last deglaciation. A fauna with characteristics similar to that of the Valdivian Rain Forest was not in place until about 13,000 yr BP. No evidence was found to support claims made from palynological studies for a pronounced episode of colder and wetter climatic conditions in the interval from about 11,000 to 9,500 yr BP. The patterns observed in the fauna began to develop about 13,000 yr BP and persisted until the present without any significant disruptions.