Canine dysautonomia was diagnosed definitively in five dogs by histopathology. All dogs were seen between June 2004 and July 2006 and originated from south-east England; four dogs originated from an urban area and one from a rural area. Of the urban dogs, one had recently visited Scotland and one had visited a kennel in a rural area nearby. Acute-onset but progressive vomiting, diarrhoea, depression and inappetence were the most common presenting clinical signs. Reduced or absent anal tone, dysuria, absence of pupillary light reflexes with intact vision, mydriasis, decreased corneal sensitivity and nictitating membrane protrusion were among the most frequent neurological findings. Abnormalities in pharmacological autonomic and physiological function testing (including orthostatic hypotension in two dogs) and diagnostic imaging studies were detected in some of the animals. All dogs failed to respond adequately to treatment, and given the poor prognosis, they were eventually euthanased. Histopathology identified marked chromatolysis of ganglion cell bodies. This case series emphasises that dysautonomia should be considered when a dog is presented in the UK with acute- or subacute-onset gastrointestinal signs and compatible physical and neurological abnormalities.