A NATO ASI on "Molecular Ecology of Aquatic Microbes" was held at II Ciocco, Lucca, Italy from 28 August - 9 September 1994. The aims of the ASI were to evaluate the potential for molecular biology to solve some important questions in aquatic microbiology, particularly in relation to biogeochemical cycling and microbial physiology. Techniques developed by molecular biologists have now been adopted by a wide range of scientific disciplines. In the last 5 years, aquatic microbial ecologists have begun to incorporate these methods into their research and, as a result, are developing a much clearer understanding of phylogenetic diversity, the molecular basis of physiological acclimations and the transduction of environmental signals and organism responses. The aim of this ASI was to assess progress in this new field of research, to compare and describe techniques and experimental approaches, and to foster communication between disciplines. The ASI offered an excellent opportunity to bring together aquatic ecologists with molecular biologists and to encourage efficient technology transfer. The meeting of information on the status provided a forum for detailed and broad exchange and trends of aquatic molecular ecology and to assess how emerging molecular techniques might solve some important problems in ecology which have prove intractable because of lack of appropriate methodologies.