TATA-binding protein (TBP) binds the minor groove of the TATA element with the DNA bent 80 degrees towards the major groove(1-4). A constrained minicircle strategy(5) has been used to test the effect of DNA topology on the affinity of TBP for the TATA element. We report here that TBP bound to DNA which was slightly pre-bent towards the major groove with 100-fold higher affinity than unbent (linear) DNA of identical sequence and 300-foId higher affinity than DNA pre-bent towards the minor groove, Similar discrimination was observed with the holo-TFIID transcription complex. DNA topology, particularly bending, is determined by many factors including chromatin in cells and may, through changes in the affinity of the TATA factor, be important in the control of transcription.