Brief considerations on the historical and clinical aspects of the Guillain-Barré syndrome are given. Two typical cases (and some suspected) were observed after an epidemy of grippe occurred in some military camps in Lisbon. The spinal fluid test showed in both cases a striking albumino-cytologic dissociation. Both had a favourable evolution. The pathogeny of the syndrome is discussed. The authors give evidence against the hypothesis of an specific virus etiology and favour the allergic theory. They think the albumino-cytologic dissociation is caused by a form of allergic serous inflammation and the Guillain-Barré syndrome would be the peripheral form (meningo-radiculo-neuritic) of the neuro-allergy.