The stratigraphy and palynology of borehole N°254 (DINAMIGE, Dirección Nacional de Geología y Minería) are described. This borehole is located in Tacuarembó Department, northeastern Uruguay. It cuts through —in ascending stratigraphic order— the San Gregorio, Melo and Yaguarí formations, late Carboniferous to Permian in age. Four palynological samples were studied and 84 species were identified. The two stratigraphically lowest samples are dominated by well-known sphenophyte, filicophyte and lycophyte species, such as Calamospora hartungiana Schopf in Schopf, Wilson and Bentall, Punctatisporites gretensis Balme and Hennelly, Leiotriletes virkkii Tiwari and Lundbladispora braziliensis Marques-Toigo and Picarelli, with less abundant gymnosperms, such as Caheniasaccites ovatus Bose and Kar emend. Gutiérrez 1993. This relative abundance relationship is gradually reversed up-section, where the gymnosperm species dominate, e.g., Lueckisporites virkkiae (Potonié and Klaus) emend. Clarke, Vittatina costabilis Wilson, Pakhapites ovatus (Bose and Kar) Playford and Dino, Vittatina vittifera (Luber) Samoilovich and Lunatisporites variesectus Archangelsky and Gamerro. This change in the palynoflora —together with shifts in sedimentary facies— is consistent with the climatic amelioration of Gondwana from peri-glacial conditions in the late Carboniferous to warm arid conditions by the middle Permian. The comparison of palynological assemblages with regional palynostratigraphic schemes suggests an age between the late Carboniferous/early Permian boundary for the San Gregorio Formation and the end of the early Permian for the Melo Formation.