The year 1894 marks the beginning of the use of diphtheria antitoxin in the treatment of diphtheria, though it was not used extensively until several years later. Since 1894, other antiserums have been produced, and other methods of nonspecific and specific protein therapy have been devised. During the last ten years, in consequence, the use of such antiserums and foreign proteins has increased enormously. In the course of this development of serum therapy, some serious and even fatal accidents have been observed. A number of fatal cases have been reported in the literature, and it may rationally be assumed that a certain number have occurred but have never been so reported. The actual number of cases in both groups is generally much overestimated. Only a few attempts have been made to compile and study the records of the reported cases. One of these, by Gottstein,1gives a brief summary