The distributional patterns of the members of the genus Nephrotoma have been analyzed. Most species prefer moist temperate climates, thus showing a correlation with the zone of deciduous forests. Almost all species of the southern hemisphere occupy strongly restricted areas in mountain forests, but the holarctic species are much more widely distributed. Within the range of the deciduous forests a number of centres can be recognized which are particularly rich in species. An exception is formed by a species-rich focus ranging from the Altai through the Baikal area, where taiga and sparsely wooded steppes intermingle. Contrary to the other centres hardly any endemics occur in this focus. The area is interpreted as a centre where species from north and south, and from east and west meet. The present distribution of the Nephrotoma species can be easily understood by postulating a radiation from eastern Asia, along with the deciduous forests, from early Tertiairy times onwards.