During six consecutive months, seven patients admitted to our ICU (15 beds, general ICU, approximately 300 intubated patients per year) for acute respiratory failure requiring intubation and mechanical ventilation presented with a peculiar neuromuscular disorder. After the occurrence of this cluster group of patients, we detected two more similar but isolated cases in the following 18 months, ie, altogether 9 patients in 2 years of observation, or 1.55 percent of all intubated patients in our ICU. Sedation was achieved using midazolam, curarization was effected with the neuromuscular non-depolarizing agent pancuronium bromide (PB), and corticosteroids were administered to eight patients. Shortly after discontinuation of sedation and curarization, we observed a persistent tetraparetic syndrome and/or peroneal palsy with a concomitant increase of serum creatine kinase (CK). None of the patients was septic or had the multisystem organ failure. A strong association between CK increase and PB administration was found, whereas no patient suffered severe liver or kidney failure. The duration of the neurologic deficit ranged from 4 to 52 weeks, with only partial recovery for some patients; the duration of dysfunction was apparently related to the total dose of corticosteroids received. Two patients had difficulty being weaned from the respirator and required tracheostomy. Electrophysiologic studies showed signs of axonal neuropathy and myopathic changes, ie, motor units of brief duration, small amplitude, overly abundant for the voluntary effort being exerted. Muscle biopsies showed significant myopathic alterations, with foci of muscle necrosis in most patients and minimal lymphocytic inflammation in one patient. The neurologic complication described differs from the polyneuropathy in critically ill patients. Furthermore, PB or corticosteroids or both appear to be the causal agents. The duration of the neuromuscular dysfunction may be related to concomitant steroid therapy. The CK enzyme seems to be a marker of the disorder. This disorder is associated with myopathic alterations and axonal degeneration in some patients. Pancuronium bromide should be used with caution, particularly when associated with steroids therapy, and it may cause difficulty in weaning patients from the respirator.