1. Total antibody in hemolysins may be estimated from the nitrogen added to sheep stromata suspensions.
2. The method is applied to a number of hemolysins and a correlation, valid to within 20 per cent, established between hemolytic titer and total antibody.
3. When stromata combine with antibody in the presence of guinea pig complement they may take up at least 80 per cent of their weight of complement combining component(s).