This paper presents a review dealing with three major aspects of a modern understanding of the disorders known collectively as the neurofibromatoses (NF). In one section, the focus is on NF heterogeneity, clarifying the distinction between NF-1, NF-2 and atypical forms of NF. In another section, the focus is on NF-1 neural-crest tumors, with particular emphasis on the four types of neurofibromas (cutaneous, subcutaneous, nodular plexiform and diffuse plexiform), schwannomas, astrocytomas and neurofibrosarcomas. In the final section, focus is on NF-1 nontumor features, both as a clinical guide and as a reminder of the breadth of concerns that a pathogenetic schema will have to consider.