Neurofibromatosis type 1 (NF1) is associated with a broad range of relatively nonspecific cognitive impairments, including low IQ, learning disabilities, and behavioral difficulties. While early studies indicated that the cognitive phenotype of NF1 resembles that of nonverbal learning disabilities (NLD), later research has found that the impairments are broader and do not fit the NLD profile well. Language‐based deficits and executive dysfunction have also been found in empirical studies. There is some evidence that neuropsychological impairment may be correlated with the underlying central nervous system involvement of NF1, but this theory has not been consistently supported across studies. Further work clarifying the cognitive phenotype of NF1 is needed, especially investigations that employ appropriate comparison groups matched for intellectual level. Am. J. Med. Genet. (Semin. Med. Genet.) 89:45–52, 1999. © 1999 Wiley Liss, Inc.