Positive reactions were obtained with 57 per cent of the sera deriving from non-paralytic patients and in 70 per cent from paralytics, when the specimens were tested at a dilution of 1:16. The complement-fixing antibody was often present in highest titer as early as 24 hours after the onset of poliomyelitis, and in almost all instances within 7 days. In about half of the patients a 4-fold or greater drop in titer occurred within 3 months, with little or no change in the others.

The incidence of titers of 1:16 or higher with the control sera varied with the season of the year at which they were procured, 3 per cent of the winter samples proving positive and 13 per cent of the summer.

The tests of sera from the group of patients from whom poliomyelitis virus was recovered, disclosed no significant differences between those having the paralytic and those having the non-paralytic disease.

Type 1 (Brunhilde-like) strains of virus were recovered from many of the patients yielding positive tests, although they presented no evidence of previous or concurrent infection with Type 2 virus. This finding shows that Type 1 virus can give rise in patients to Type 2 complement-fixing antibody.

The application of these data to the serologic diagnosis of poliomyelitis infection in man will of necessity be limited until information is obtained on the development, persistence, and significance of complement-fixation reactions with antigens deriving from Type 1 and Type 3 poliomyelitis strains.