The pseudogap phenomenon in high-T-c superconductors

We review the possible mechanisms leading up to the phenomenon of a pseudog ap which characterizes the normal-state properties of high-T-c superconduct ors. We suggest that this pseudogap is not due to superconducting phase flu ctuations and hence is not related to a crossover between a BCS state of Co oper pairs and a Bose-Einstein condensation of local pairs. We rather argue that it is due to uncorrelated pairing which is already manifest in the lo cal electronic structure and accessible by photoemission and tunneling expe riments.