Abstract
Characteristics of a Mycobacterium intracellulare reference precipitation system for immunodiffusion and immunoelectrophoresis analyses are presented. The system was produced by the initiative of the International Working Group on Mycobacterial Taxonomy, and the purpose is to permit comparisons of precipitinogenic patterns of mycobacteria obtained in different laboratories. The reference material, consisting of an antigen preparation and a corresponding antiserum, is available for students of mycobacterial antigens in accordance with guidelines adopted by the Working Group.