The mutant gene causing von Recklinghausen neurofibromatosis (NF1) was recently shown to map to chromosome 17. We have used additional markers for chromosome 17 to narrow further the location of the gene defect. A preliminary multipoint linkage analysis suggests that the NF1 gene is located on the long arm of chroomsome 17, flanked by D17Z1 and NGFR. Linkage analysis with the human oncogene homolog erbA1, which maps to this region, suggests that this cancer-related gene is not the primary cause of NF1.