This is the third volume of Advances in Microbial Ecology to be produced by the current editorial board. I would, therefore, like to take this opportunity to thank my co-editors for all their efforts, particularly in maintaining a balance of subject matter and geographical distribution of the contributions. Volume 15 is no exception in that we have a balance between the prokaryo tic and eukaryotic organisms and a range of subject matter from applied ecology through process ecology to ecological theory. The response from our readers has been encouraging in the sense that the breadth of coverage is much appreciated, particularly by teachers and postgraduate/postdoctoral researchers. However, we still strive to improve our coverage and particularly to move wider than the North America/Europe axis for contributions. Similarly, we would like to see coverage of the more unusual microbes, perhaps a chapter devoted to the ecology of a particular species or genus. There must exist many ecological notes on "rarer" organisms that have not found their way into the standard textbooks or taxonomic volumes; properly compiled these could provide valuable information for the field ecologist. Ecological theory has, until recently, been the domain of the "macroecolo gist. " Recent advances in molecular techniques will ensure that the microbial ecologist will playa more significant role in the development of the subject. We shall not, therefore, change our policy of encouraging our contributors to specu late, permitting them sufficient space to develop their ideas.