OBJECTIVE Because the aminoglycoside antibiotics and nondepolarizing muscle relaxants have interactions that vary, it is necessary to update the potential for such interactions when new drugs are introduced clinically. Rocuronium is a newly released steroidal nondepolarizing muscle relaxant with an intermediate duration of action. The following report is the first description of prolonged neuromuscular blockage after rocuronium in a patient who had received oral neomycin in anticipation of open bowel resection. METHODS A 71-yr-old woman with a two week history of bleeding pr was scheduled for exploratory laparotomy and right hemicolectomy. She received two standard bowel preparations consisting of oral erythromycin and neomycin over a two day period. Rocuronium was used to facilitate tracheal intubation and maintain muscle relaxation during a two hour operation. Despite clinical appearance of reversal of neuromuscular blockade after neostigmine and glycopyrolate, the patient complained of dyspnoea and weakness upon tracheal extubation and required reintubation twice. The reason for prolonged muscle relaxation was thought to be secondary to a rocuronium and neomycin interaction. CONCLUSIONS Rocuronium, a new nondepolarizing muscle relaxant, has potential interactions with other drugs including the aminoglycoside antibiotics. This clinical report describes the failure of neuromuscular blockade reversal in a patient who received oral neomycin in anticipation of open bowel resection.