Sommerfeld Theory Colloquium, The conjectured relation between higher spin theories on anti de-Sitter (AdS) spaces and weakly coupled conformal �field theories is reviewed. I shall then outline the evidence in favour of a concrete duality of this kind, relating a speci�c higher spin theory on AdS3

to a family of 2d minimal model CFTs. Finally, I shall explain how

this relation �ts into the framework of the familiar stringy AdS/CFT correspondence.