Two male patients 46 and 44 y.o. respectively, were admitted for a syndrome of chronic pain characterized by: sudden onset, spontaneous or following spasmodic coughing, of an anterior hemithoracic pain slowly progressing to involve several unilateral cervicothoracic dermatomes, a continuous burning sensation made worse by light touch, limb movements and cold water, and partially relieved by warm water or deep palpation. On examination, patient 1 revealed no sensorimotor deficit after repeated observations during 8 years. At autopsy, a syrinx localized at the cord segments corresponding to the symptoms was found without documentation of specific causal factors. It involved the posterior horn of the cord selectively. In patient 2, pain was associated with slight hypesthesia to pinprick and heat from C2 to T5 on the left without motor deficit since 18 months. A high resolution C.A.T. scan showed an intramedullary cavity 0.3 cm from the midline in the projection of the posterior horn without anomalies at the cervicomedullary junction. These observations link chronic pain syndromes with predominantly posterior horn lesions, which so far have failed to respond to conventional therapeutic measures.