Microbial mats are benthic communities of a variety of microorganisms. Their investigation requires multidisciplinary studies and close cooperation between microbiologists, biogeochemists, and geologists. Reported here are recent advances in the study of structure, development and ecological relationships. The methodology described includes microsensors as well as new molecular techniques for the detection and identification of microorganisms. Increasing interest exists for applied aspects, e.g. the possibility to use natural or constructed microbial mats for the degradation of xenobiotics, for site remediation, etc.Proceedings of the NATO Advances Research Workshop on Structure, Development and Environmental Significance of Microbial Mats, held in Arcachon, France, September 27 - October 1, 1993Microbial mats are benthic communities of a variety of microorganisms. Their investigation requires multidisciplinary studies and close cooperation between microbiologists, biogeochemists, and geologists. Reported here are recent advances in the study of structure, development and ecological relationships. The methodology described includes microsensors as well as new molecular techniques for the detection and identification of microorganisms. Increasing interest exists for applied aspects, e.g. the possibility to use natural or constructed microbial mats for the degradation of xenobiotics, for site remediation, etc.Opening lecture.- Microbial mat research: The recent past and new perspectives.- I. Colonization and initial processes in mat formation.- Microbial mats in coastal environments.- Species diversity in hot spring microbial mats as revealed by both molecular and enrichment culture approaches relationship between biodiversity and community structure.- Microbial mats in a thermomineral sulfurous cave.- Establishment of phototrophic purple sulphur bacteria in microbial mat systems.- Biological versus inorganic processes in stromatolite morphogenesisl³D