A short review of the literature on the stratigraphy of the Devonian and the Lower Carboniferous of the Cantabrian Mountains precedes the report of the author's stratigraphic and palaeontologic observations in León: the Río Esla area (Gedinnian to Viséan), the central Cantabrian area (Famennian to Viséan), and the Gildar-Montó area (Eifelian to Viséan); in Asturias: the coastal area (Frasnian to Viséan); in Palencia: the Arauz-Polentinos area (Gedinnian to Givetian), the Carda\u0148o-Triollo area (Eifelian to Viséan), and the San Martín-Valsurvio area (Givetian and Famennian to Viséan); and in Santander: the Liébana area (Eifelian to Viséan). Most of the conodont faunas, which were extracted from calcareous formations, could be arranged in the zonal succession established in Germany, and thus supplied new data about several formations in the Cantabrian Mountains. The presence of the transgressive Ermita Formation in Asturias and Palencia is demonstrated. The age of this unit ranges maximally from uppermost Famennian to lowermost Tournaisian. The Carda\u0148o Formation ranges from middle or upper Givetian to upper Frasnian. The Vidrieros Formation ranges from the upper part of the lower Famennian to the lowermost Tournaisian. A synthesis of the stratigraphic data delimits the Palentine facies area, which is clearly separated from the Asturo-Leonese facies area by positive areas. The following palaeogeographic units are distinguished: the Asturo-Leonese Basin, the Palentine Basin, and the Asturian Geanticline. The development of these units from the Middle Devonian to the Lower Carboniferous is demonstrated by eight facies-pattern maps. The sedimentation on the Asturian Geanticline was limited and probably incomplete. An epeirogenetic uplift of this geanticline took place in late Frasnian to early Famennian times. This uplift is correlated with the deposition of the quartzitic Murcia Formation in the sheltered Palentine Basin. The uplifted area was covered by the Ermita transgression in the late Famennian to early Tournaisian. After a break in the sedimentation, a local transgression resulted in the Vegamian Formation in the upper Tournaisian. In most of the area the Alba transgression began in the uppermost Tournaisian or lower Viséan. In the Palentine Basin the deposition of the Alba Formation started in the upper Viséan. The chapter on systematics deals mainly with the most important zonal guide forms of the conodonts. Three new elements are described: Icriodus eslaensis n.sp. from the middle to upper Givetian, Siphonodella? n.sp. a, probably from the upper Tournaisian, and n.gen. A n.sp. a, a simple compound conodont from the upper Gedinnian or lower Siegenian.