A model of the Ancestral stage (2 to 1 Ma) at the Nevado del Ruiz Volcano is proposed. The extension of the lava remnants of this stage covered an area of about 200 Km 2 and they were cartographied around the Northeast-North-Northwest of the present edifice of the volcano. Whole-rock geochemical data of andesitic, basaltic-andesitic and dacitic samples from the different outcrops share the calcalkaline affinity with medium to high K contents. The trace elements range variation compared with SiO 2 suggests a fractional crystallization mechanism from the ferromagnesian minerals and the calcic plagioclase. The trace elements pattern is typical of a volcanic arc with Sr, K, Rb, Ba y Th enrichments and Nb impoverishment. The REE diagram shows a smooth slope and the typical LREE enrichment.