We report on a patient with acute-onset facial and bulbar palsy that deteriorated within a week needing ventilatory support. He was initially treated for Guillain-Barre syndrome in view of the acute onset and non-fluctuating course of illness, absence of previous history of palsy, and acute respiratory decompensation. The patient’s tensilon test was negative but his acetylcholine-receptor antibody titre was high, confirming a diagnosis of myasthenia gravis. There were no associated features of thymoma. He responded well to pyridostigmine and prednisolone.