Neurofibromatosis (NF) is a disease of protean manifestations involving tissues of ectodermal and mesodermal origin. Modern terminology divides NF into NF-1 (classically peripheral NF) and NF-2 (classically central NF). Gene linkage will provide many answers to understanding the varied and unpredictable course of NF. Gene linkage may explain phenotypic variations among NF patients, malignant transformation potential of neurofibromas, increased likelihood of malignant sarcomas in NF patients, and possible insight into learning disability in NF patients. Chromosome location has been narrowed to the pericentric region of chromosome 17 for NF-1 and to the center of the long arm of chromosome 22 for NF-2.