Three 8-week-old Miniature Smooth Haired Dachshund littermates were diagnosed with myasthenia gravis based on clinical signs, results of electrophysiological testing, and response to the short-acting anticholinesterase drug, edrophonium chloride. Congenital myasthenia gravis was confirmed by the demonstration of decreased acetylcholine-receptor density in external intercostal muscle in the absence of demonstrable serum antiacetylcholine receptor antibody or antibodies complexed to acetylcholine receptors in muscle biopsy samples. Unlike most previously reported cases of congenital myasthenia gravis that are relentlessly progressive, clinical signs resolved spontaneously by 6 months of age.