Hemagglutination test of tuberculin sensitized red cells on serum of patients of erythema nodosum leprosum revealed the following results.
1. High agglutination titre was not always proved in all periods of erythema nodosum leprosum.
2. In typical type, the maximum titre usually occurred at a few days after the temperature had fallen.
3. In atypical type, the maximum titre usually occurred between the 7th and 14th day, but the curve of titre was irregular.