We describe FST - a Framework for SDF Transformation. FST supports the adaptation (in a broad sense) of grammars based on the syntax definition formalism SDF. The executable specification of FST is based on the ASF+SDF Meta-Environment. Grammar transformations form an important concept of grammar reengineering, implementation, recovery and others. Tool support for grammar transformations is essential to automate the corresponding processes. We have chosen SDF as target language for grammar transformations because it is an expressive syntax definition formalism which does not just cover BNF and extended BNF but also constructs for modularisation and disambiguation. The algebraic specification of the framework is immediately operational in the ASF+SDF Meta-Environment.