PALYNOLOGY OF THE PERMIAN OF THE CLAROMECÓ-COLORADO BASIN, ARGENTINA. We present a paleopalynological study of samples obtained from two boreholes (UTAL.CMM1. La Estrella x-1 and UTAL.CMM1. Cruz del Sur x-1) of the Claromecó-Colorado Basin, referred to Piedra Azul, Bonete and Tunas formations (Pillahuincó Group), which are Permian in age. One hundred and thirty-one species of spores (trilete and monolete), prasinophyte algae, acritarchs, fungi and pollen grains (monosaccate, bisaccate, striate and monosulcate) have been recorded. We also propose a new species Lunatisporites coloradensis sp. nov., and Falcisporites parvus (de Jersey) comb. nov., Falcisporites similis (Balme) comb. nov. and Tiwarisporis anaverrucosus (Archangelsky and Gamerro) comb.nov.. Two associations referred to a Cisuralian—Guadalupian age (Association I) and a Guadalupian—Lopingian age (Association II) are identified based on previous stratigraphic records of the identified species. The associations also show a variation in the proportions of the palynological components, showing a change in the environmental conditions, which range from a more favourable and humid period to another one characterized by water shortage and increase of the aridity.