When the Spanish edition of this book was reveiwed in The Journal, July 14, 1945, the desirability of an English translation was mentioned. This has been done, so that the book is available to a larger audience than was formerly the case. It is the most extensive treatise on myasthenia gravis published in recent times. The number of cases is relatively small but they are well reported. There is an adequate history of the development of our knowledge of the disease. A chapter on pathologic physiology, published in collaboration with Alfredo Lanari, an investigator who has worked both in this country and in Buenos Aires, adds greatly to the value of the book.