In previous reports1 we presented an analysis of the findings of a controlled field study2 on the prevention of paralytic poliomyelitis by gamma globulin. The diagnosis of the cases included in these earlier reports was based entirely on rigid clinical criteria previously outlined,2a since no laboratory data were available at that time. The accuracy of such criteria has never been completely evaluated, because suitable laboratory tests have only recently become available, but errors in etiological diagnosis were to be expected even though only paralytic cases were included. In this paper we are presenting a reanalysis of results based exclusively on laboratoryconfirmed cases. We shall also make reference to the United States Public Health Service reports3 concerning the general use of gamma globulin in 1953 as they relate to data from our controlled study.
Infection with poliomyelitis virus can be determined by either of two