Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) form a spectrum of clinically, pathologically, and genetically overlapping disorders, as confirmed by the recent report that it can be caused by a hexanucleotide repeat expansion in C9orf72. One hundred and fourteen Portuguese cases diagnosed as probable or possible familial FTLD, as part of the EOD consortium study, and nine further Portuguese cases with familial ALS were tested for the presence of this mutation. Results showed that six Portuguese patients from unrelated families had the mutation, five (4.4%) patients from the FTLD group and one (11.1%) from the ALS sample. Of these, three patients had FTLD and rapidly progressive bulbar ALS. Electromyography confirmed diffuse loss of motor units with marked bulbar involvement. In conclusion, the cases now reported showed a very rapid progression, suggesting bulbar ALS could be particularly common and aggressive in patients with the C9orf72 hexanucleotide repeat expansion, in the Portuguese population.