The physics potential of a high-energy photon collider is reviewed. The emphasis is put on aspects related to the symmetry breaking sector, including Higgs searches and production of longitudinal vector bosons. ENSLAPP-A-527/95 arch-ive/9508218 June 1995 § URA 14-36 du CNRS, associée à l’E.N.S de Lyon et à l’Université de Savoie. Talk presented at the Photon’95 Conference, Sheffield, England, A...