We are most gratified by the response to the initiation of this series of volumes presenting recent developments and new concepts in microbial ecology. Favorable reactions have been expressed in both oral and written communication, and Ad- vances in Microbial Ecology thus seems to be providing a worthwhile outlet in a rapidly growing field of microbiology and environmental sciences. The growing importance of microbial ecology is evident in many ways. Uni- versity personnel are expanding their programs and increasing the number of research topics and publications. Substantial numbers of industrial scientists have likewise entered this field as they consider the microbial transformation of chemicals in waters and soils and the effects of synthetic compounds on natural microbial communities. Agricultural, medical, dental, and veterinary practitioners and scientists have also been increasing their activity in microbial ecology because of the importance of the discipline to their own professions. In addition, govern- mental agencies have expanded regulatory and research activities concerned with microbial ecology owing to the importance of information and regulations fo- cused on the interactions between microorganisms in nature and particular en- vironmental stresses.