Two forms of neurofibromatosis are currently described. Von Reckinghausen Neurofibromatosis (NF 1) is the classic and common form, recently localised to chromosome 17. Neurofibromatosis type 2 (NF 2) or bilateral acoustic Neurofibromatosis, formerly the "central form" of von Reckinghausen disease, is characterized by multiple brain tumors, most often bilateral acoustic neuromas. The NF 2 mutation lies on the long arm of chromosome 22. The two forms predispose to benign or malignant familial tumors, derived from neural crest germ lines, such as Schwann cells. Rapid progress in the understanding of mechanisms underlying neurological tumor formation is expected in these inherited diseases. Molecular biology will allow the precise identification of genes responsible for the neurofibromatose syndromes. Practical applications, such as screening of individuals at risk for the disease will soon be available. Medical follow-up and genetic counselling should improve as a result of these advances.