Most mesenchymal tumors originating from the gastrointestinal tract are gastrointestinal stromal tumors (GIST), with an estimated incidence of approximately 10-15/1.000.000. This book of six chapters from international experts opens with and overview of disease pathophysiology and drug targets for GIST. There then follow detailed chapters on notable tyrosine kinase inhibitors for the disease and on inhibitors currently in clinical evaluation. The closing chapter explores other tyrosine kinase inhibitors currently in the pipeline and points the way for future directions for therapy.