It was reported previously that guinea pigs sensitized with M. leprae were converted to positive reaction with the use of not only Dharmendra antigen but also tuberculin and guinea pigs sensitized with human tubercle bacilli or BCG too were converted to positive reaction due to tuberculin and Dharmendra antigen. On the other hand, it was found that the positive conversion of reaction due to Dharmendra antigen were primarily effected with BCG vaccination and secondarly with the natural infection of tuberculosis, investigating on the results of reaction due to Dha-rmendra antigen among general population.
Then, for the investigating on the problem whether the infection of leprosy could be detected with the use of Dharmendra antigen, the results of reaction due to Dharmendra antigen among people of leprosy-household were compared with those in the othe populations. The results obtained were as follows;
1) The ratio of Dharmendra positive rate to tuberculin positive rate and the positive rate of reaction due to Dharmendra antigen among tuberculin positive reactors was higher in peoples of the leprosy-household than in the other populations.
2) The positive rate of reaction due to Dharmendra antigen among tuberculin negative reactors was significantly higher in peoples of the leprosy-household than in the other populations.
These above results may be suggested that the positive conversion of reaction due to Dharmendra antigen can be carried out by means of the infection of leprosy.
Then, the relationship between the results of reaction due to Dharmendra antigen among general populations and the incidence of leprosy was investigated. As a result, it was clarified that the reaction due to Dharmendra antigen might be useful for the detection of immunity against leprosy and for discovering the incidence of leprosy epidemiologically, if the positive rate of reaction due to Dharmendra antigen was investigated under the consideration of the tuberculous infection or the inoculation with BCG.

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