Undoubtedly the largest attempt at prophylaxis against epidemic influenza through the use of “mixed vaccines” was that made under the direction of Dr. W. O. Sherman for the Carnegie Steel and H. C. Frick Coke Companies. The results which Dr. Sherman hoped to attain when he planned using the vaccine and collecting the data have already been given. Commercial mixed vaccines similar to those described under the “Series I” experiment were used, and four doses, three days apart, were given. Inoculations were begun on October 20, 1918, and were completed during the first week of November. Vaccine was administered to the employees and their families without charge. Later cards were given to all employees, and they were made to fill them out and return them. On the cards were blanks calling for the name, age, sex, color, number of inoculations, whether or not the employee himself or any member of his family had had influenza, and how many days the sick individuals had been in bed. Each mill and mine was then supplied with a set of blank forms providing for a complete statistical record of the number of inoculations and the total incidence of influenza, pneumonia and death. From the reports of the respective mills and mines the total figures given in the charts were compiled. Difficulties were encountered in every part of the work. The vaccine demand was so great that the products of three different firms were used. So many doctors were in service that most of the vaccine had to be given by carefully coached nurses. The bulletins of the United States Bureau of Public Health and of the Allegheny County Medical Society, with their warnings about influenza vaccines being only in the experimental stage, appeared just at the time the work was begun and caused a great many to refuse to complete vaccination after one or two doses had been given. So few medical men were left that it was impossible to have them see all cases and so determine the nature of many of the illnesses which were occurring. It was assumed, therefore, that any employee who had fever and was sick for a period of three days had influenza, and that any who were confined to bed for seven days or more had pneumonia. The figures of the central offices were made up from the reports of 14 steel mills, 1 cement factory, 4 warehouses and 57 mining districts. The accuracy of data depended on the careful work of a great many local statistical workers, which made individual variations hard to control. The greatest difficulty of all, however, lay in finding a common basis for comparisons of the incidence of influenza, pneumonia and death in the vaccinated and non-vaccinated groups, since the data on the former group included the occurrence only after the peak of the epidemic had been passed, and that of the latter group included the occurrence for the entire epidemic. The total figures are given in the three charts. CHART I.