A clinic case of amyotrophic lateral sclerosis (ALS) in a 51 years old woman is reported. The patient exhibited signs of pyramidal system and anterior motor neuron involvement. The cerebrospinal fluid examinations showed clear cut indications of parenchymatous neurosyphilis. Attention is called to the rarity of the association above mentioned. The role of neurosyphilis as an atiological factor of ALS is discussed. The authors conclude that in the case described there is a close relationship between the two entities.