The Union is composed of three Divisions, each concerned with a major microbiological science. The Divisions are administratively responsible for Committees, Commissions and Federations (hereafter referred to as COMCOFs) each concerned with a particular aspect of microbiology

IUMS consists of three Divisions. Each of them have an Executive Board and they organize their own congresses. BAM and Mycology organize their congresses jointly, while Virology has its own congress.

Bacteriology & Applied Microbiology (BAM) Division

The aims of the Division of Bacteriology and Applied Microbiology are to further bacteriology and related sciences throughout the world in research, education and services

Mycology and Eukaryotic Microbiology (MEM) Division

The aims of the Division of Mycology and Eukaryotic Microbiology are to further the discipline of eukaryotic microbiology, incl. mycology and all branches of research related to it: establish and maintain contact among eukaryote microbiologists by spon­soring international congresses, symposia, conferences and colloquia; distribute information; encourage research and training. The Division has links and a strong collaboration with the International Mycological association (IMA).

Virology Division

lts aims are to further the discipline of virology and all branches of science related to it; encourage contact among virologists; foster interchange of information through sponsorship of international congresses and symposia.