The results of the dehydration of C-5-raw material to obtain furfural via heterogeneous catalysis in water are discussed. Furfural has the potential to substitute fossil compounds on a large scale for polymers, solvents, fine chemicals and finally fuels. Industrial catalysts were reviewed and new catalysts were synthesized. The main difference to recent work is the abdication of supercritical fluids, organic solvents, phase modifiers and ionic liquids. With this also the contamination of the product is prevented and higher product qualities are obtained.