Critical illness polyneuropathy (CIP) is a reported cause of varying degrees of neuromuscular weakness in patients with multiple organ failure. Little is known concerning predictive factors of neurological recovery. The critical care conditions, neurological explorations and 2-year clinical follow-up of 19 patients who suffered from severe forms (quadriplegia or quadriparesis) of CIP were analyzed. Characteristics of patients who recovered clinically were compared with those of patients who did not. Two patients died within 2 months, 11 recovered completely, 4 remained quadriplegic and 2 remained quadriparetic. All patients suffered from sepsis, multiple organ dysfunction syndrome and a catabolic state before the onset of CIP. Outcome appears difficult to predict with clinical or electrophysiological data. Three parameters were significantly correlated with poor recovery: longer length of stay in the critical care unit, longer duration of sepsis and greater body weight loss. A relationship seems to exist between the severity of CIP and that of sepsis and its associated hypercatabolism. The favorable outcome usually attributed to CIP must be reconsidered. The authors recommend aggressive measures against sepsis to limit CIP and its sequelae.