Finland, located at the edge of the inhabitable world, is one of the best-studied genetic isolates. The characteristic features of population isolates-founder effect, genetic drift and isolation-have, over the centuries, shaped the gene pool of the Finns. Finnish diseases have been a target of extensive genetic research and the majority of some 35 disease genes enriched in this population have been identified; the molecular and cellular consequences of disease mutations are currently being characterized. Special strategies taking advantage of linkage disequilibrium have been efficiently used in the initial mapping and restriction of Finnish disease loci and this has stimulated development of novel statistical approaches in the disease gene hunt. Identification of mutated genes has provided tools for detailed analyses of molecular pathogenesis in Finnish diseases, many of which reveal a distinct tissue specificity of clinical phenotype. Often these studies have not only clarified the molecular detail of Finnish diseases, but also provided novel information on biological processes and metabolic pathways essential for normal development and function of human cells and tissues.