Mycoplasma pneumoniae infection in a 47-year-old man is reported. Symptoms of upper respiratory tract infection were followed by pneumonia and meningoencephalitis. In contrast to published cases with neurological manifestations of infection with M. pneumoniae, the patient was disabled by persistent cerebellar symptoms with generalized ataxia and atactic dysarthria. Some possible pathogenic mechanisms of the neurological manifestations of infection with M. pneumoniae are considered.