The Guillain-Barré syndrome associated with cytomegalovirus infection is a recognized entity of unknown pathogenesis. We observed two characteristic cases with acute polyradiculoneuropathy which occurred after renal transplantation. Both patients fulfilled the diagnostic criteria for Guillain-Barré syndrome: tetraparesis with diffuse areflexia and moderate sensorial signs, high protein level in cerebrospinal fluid without cellular reaction, slow or blocked nerve conduction and partial cure after several months delay. In two-thirds of such cases, the syndrome follows an episode of infection. Cytomegalovirus has been recognized as a possible association. The demyelinating polyradiculoneuropathy induced by cytomegalovirus has been reported essentially in immunodepressed patients infected with the human immunodeficiency virus in whom a pathogenic role for cytomegalovirus in peripheral nerves has been suggested. In our two cases, the cytomegalovirus infection occurred before onset of the acute polyradiculoneuropathy. In both cases, specific IgM antibodies and clear IgG positivization occurred before the first signs of neurological impairment even though neither the virus nor specific antibodies could be concomitantly detected in the cerebrospinal fluid. Despite the frequency of cytomegalovirus infections in transplant recipients, to our knowledge, only 9 cases of Guillain-Barré syndrome after transplantation have been reported and the exact mechanism remains to be ascertained. These two cases suggest that the onset of the Guillain-Barré syndrome after renal transplantation was closely related to cytomegalovirus infection. Adequate measures should be taken to quickly diagnose such cases in order to instore rapid treatment for the polyradiculoneuropathy. In addition, this particular situation of post-transplantation onset might help better understand the exact role of cytomegalovirus infection in the Guillain-Barré syndrome.