Numerous kindreds with familial frontotemporal dementia and/or amyotrophic lateral sclerosis have been linked to chromosome 9 (c9FTD/ALS), and an expansion of the GGGGCC hexanucleotide repeat in the noncoding region of chromosome 9 open reading frame 72 (C9ORF72) was identified in the summer of 2011 as the pathogenic mechanism. An explosion of papers on this disorder is in progress, and a relatively distinctive phenotype is taking form. In this review, we present an illustrative case and summarize the demographic, inheritance, clinical and behavioral aspects of c9FTD/ALS based on the available data on over 250 patients with behavioral variant FTD +/- parkinsonism +/- ALS.