Extreme environments provide a unique source of often highly adapted and tolerant organisms. Research on organisms in these habitats has led to the discovery of novel and useful compounds and may assist in understanding the impact of global change on biodiversity. The Dry Valleys of Eastern Antarctica are vast, ice-free regions believed to be the coldest, driest desert on Earth. Despite these harsh conditions, there is an increasing amount of evidence demonstrating that the soil ecosystems of the Dry Valleys sustain a wide diversity of microorganisms. The research presented is an inter-valley comparison study which aims to scrutinize microbial communities and environmental factors driving their distribution in the Dry Valleys. Automated ribosomal intergenic spacer analysis (ARISA) was used to provide a snapshot of bacterial and cyanobacterial communities living in the mineral sands in Miers Valley, Beacon Valley, Upper Wright Valley and at Battleship Promontory. Rigorous analysis of physico-chemical differences between the soils of these four valleys was undertaken in hope to understand the environmental parameters driving the distribution and biodiversity of microbial communities present. Multivariate statistical analysis and ordination of ARISA and physico-chemical data revealed that bacterial communities from each valley form distinctive clusters. Conversely, cyanobacterial communities showed less diversity and a more even distribution between valleys.