The oncofetal Thomsen-Friedenreich carbohydrate antigen (Galbeta1-3GalNAcalpha1-Ser/Thr TF or T antigen) is a pan-carcinoma antigen highly expressed by about 90% of all human carcinomas. Its broad expression and high specificity in cancer have attracted many investigations into its potential use in cancer diagnosis and immunotherapy. Over the past few years increasing evidence suggests that the increased TF occurrence in cancer cells may be functionally important in cancer progression by allowing increased interaction/communication of the cells with endogenous carbohydrate-binding proteins (lectins), particularly the members of the galactoside-binding galectin family. This review focuses on the recent progress in understanding of the regulation and functional significance of increased TF occurrence in cancer progression and metastasis.