Botulism is a neuroparalytic disease caused by neurotoxins produced by Clostridium botulinum. Food-borne botulism is a kind of exotoxin-caused food intoxication. Although this disease is rarely reported in Japan now, it is a cause of great concern because of its high mortality rate, and botulism cases should be treated as a public health emergency. Botulism classically presents as acute symmetrical descending flaccid paralysis. Its diagnosis is based on the detection of botulinum toxins in the patient's serum or stool specimens. Electrophysiologic tests of such patients show reduced compound muscle action potentials (CMAPs), low amplitudes and short durations of motor unit potentials (MUPs), and mild waning in repetitive low-frequency stimulations. Single fiber electromyography (EMG) is particularly useful for the diagnosis of botulism. We report a case of food-borne botulism that we had encountered. An 83-year-old man with rapidly progressive diplopia, dysphagia, and tetraplegia was hospitalized; he required intensive care, including artificial ventilatory support. Electrophysiologic tests yielded findings compatible with botulism. We made a clinical diagnosis of food-borne botulism and administered antitoxin on the seventh disease day. The patient's motor symptoms started ameliorating several days after the antitoxin injection. Subsequently, botulinum toxin type A was detected in the patient's serum specimen by using a bioassay, and the type A gene and silent B gene were detected in his serum specimen by using polymerase chain reaction (PCR). C. botulinum was also obtained from stool culture on the 17th and 50th disease days. Botulism is a curable disease if treated early. Although it is a rare condition, it should always be considered in the differential diagnosis of patients with rapid onset of cranial nerve and limb muscle palsies.