The 16th International Workshop on Implementation and Application of Fu- tional Languages (IFL 2004) was held in Lub ] eck, Germany, September 8 10, 2004. It was jointly organized by the Institute of Computer Science and Applied Mathematics of the University of Kiel and the Institute of Software Technology and Programming Languages of the University of Lub ] eck. IFL 2004 was the sixteenth event in the annual series of IFL workshops. The aim of the workshop series is to bring together researchers actively engaged in the implementation and application of functional and function-based progr-...