The very complex and specific knowledge about inborn errors of metabolism increases rapidly and is spread worldwide. Therefore an Internet platform for the acquisition of statistical knowledge (PATDB) and for the collection of the experience of experts (Metabolic diseases database) has been established. The success of diagnostic support highly depends on the way of knowledge representation. An information retrieval system for physicians will offer first insights about useful user interfaces and handling properties. Furthermore information fusion of biomedical systems to a Biomedical Workbench for the simulation of biochemical reactions is described.