Case-1: A 24-year-old woman was admitted because of pressing hydramnion. She was treated by ritodrine hydrochlorides leading to rhabdomyolysis, and she was diagnosed as myotonic dystrophy. She underwent cesarean section because of urgent premature birth. The surgery was performed with spinal anesthesia using tetracaine. Case-2: A 1-year-old boy, the son of Case 1, underwent orchiopexy. He showed respiratory distress at birth and needed respiratory support for 140 days. The surgery was performed under general anesthesia combined with caudal anesthesia. Anesthesia was induced with nitrous oxide-oxygen-sevoflurane. He was intubated without muscle relaxants. Since he recovered consciousness soon after the surgery, he was extubated and returned to the ward. Case-3: A 30-year-old woman, the sister of Case 1, underwent tonsillectomy. At the age of 27 she underwent salpingectomy under general anesthesia with nitrous oxide-oxygen-halothane, after which she was diagnosed as myotonic dystrophy. She was anesthetized with propofol and fentanyl. Because severity of the myotonic dystrophy varies among the patients, the strategy for anesthesia should be planned on each patient. Generally speaking, regional anesthesia including spinal and epidural anesthesia is preferable.