A seven-month-old male collie was brought to our clinic with complaints of exhaustaion and fatigue for the past month, inability to stand on its hind legs, loss of voice and anorexia for the past week, in clinical examination. increase in heart frequency, difficulty in lifting the head, tetraparesis, regurgitation and urinary incontinence were observed. MG was suspected and 0.05 mg/kg i.m. neostigmine methylsulfate was given for clinical diagnosis. A positive response was seen within 30 minutes of drug application. The same drug was administered 3 hours later and the same positive clinical findings were observed. The disease was diagnosed as MG. The serum AChR antibody concentration was determined to be 0.03 nmol/l. Pyridostigmine bromide was used for four weeks and prednisolone was used for two weeks. The patient was able to walk normally after 15 days and had a good appetite. The dog was sent back home in good health six weeks later and the disease did not relapse for more than two years.