This thesis deals with the Six Sigma and LEAN project management methodology and its mutual linkage to Lean Six Sigma. In the first part it describes its basic theoretical principles explaining the background and the roots of both approaches. Furthermore, the adaptation to SAP Sigma is brought to light. In the practical part a case study of the application of Six Sigma on a project called FastClose is introduced and investigated. In addition, Lean Six Sigma methods are applied as well in order to explore further improvement potential within the project.