This study is an extension of a previous study on an antileprosy combination vaccine of BCG plus killed Mycobacterium leprae (KML) regarding its sensitization potential and reactogenicity. The study was extended to see if by reducing the dose of BCG in the combination vaccine the incidence of suppurative adenitis could be reduced without a significant reduction in the level of postvaccination skin-test responses. The study included 860 individuals, and three preparations of the combination vaccine [BCG 0.05 mg + 6 x 10(8) KML (I), BCG 0.05 mg + 5 x 10(7) KML (II), BCG 0.01 mg + 5 x 10(7) KML (III)] along with normal saline (i.v.) were used. Each individual received one of these four preparations by random allocation. They were also tested with Rees' M. leprae soluble antigen (MLSA) and lepromin A 12 weeks after vaccination. Reactions to the MLSA were measured after 48 hr; reactions to lepromin A after 48 hr and 3 weeks. The character and size of the local response at the vaccination site were recorded at the third, eighth, and 15th week postvaccination. The results of the study showed that by halving the dose of BCG in the combination vaccine BCG plus 6 x 10(8) KML a) the incidence of suppurative regional adenitis was reduced significantly, b) there was no significant change in the post-vaccination response at 12 weeks as measured by Rees' MLSA and lepromin A, and c) the evolution of the vaccination lesion was somewhat prolonged. This dose was found satisfactory for use in a comparative antileprosy vaccine trial in South India.