Book excerpt: This book contains updated reviews and original research work on Down Syndrome focussing on brandnew results in neurobiology, in particular results on gene hunting (subtractive hybridization, differential display) and neurochemistry. The book provides new data such as a subtractive library of Down Syndrome brain showing cDNAs that are overexpressed or downregulated and can be regarded as a source for further research on the preliminary transcriptional data given. A 2D-electrophoretic map of human brain proteins including Down Syndrome brain protein expression established by in-gel-digestion of spots with subsequent MALDI-identification provides the scientific basis for protein work to the neuroscientist. Altogether, the book provides a series of new candidate genes possibly involved in Down Syndrome neurobiology, tools for neuroscience studies on Down Syndrome brain thus serving as a manual and updated views and aspects on Down Syndrome pathobiology.