The use of microorganisms and their metabolic products to stimulate oil production is currently receiving renewed interest worldwide. This technique involves the injection of selected microorganisms into the reservoir and the subsequent stimulation and transportation of their in situ growth products, in order that their presence will aid in further reduction of residual oil left in the reservoir after secondary recovery is exhausted. Although unlikely to replace conventional microbial enhanced oil recovery, this unique process seems superior in many respects. Self-duplicating units, namely the bacteria cells, are injected into the reservoir and by their in situ multiplication they magnify beneficial effects.This new approach to enhancement of oil recovery was initiated in 1980 and the first results were published in the proceedings of two international conferences. This book evolved from these conferences, and was designed to encompass all current aspects of microbial enhanced oil recovery: the development of specific cultures, increase of the population for field application, various methods for field applications and the results, and the environmental concerns associated with this newly developed technology. It provides a comprehensive treatise of the subject, and is arranged to show the laboratory development of microbes suited to microbial enhanced oil recovery and the perpetuation of the special cultures in a petroleum reservoir. Thus, this book has specific usefulness in the laboratory, the oilfield and the classroom. Although not written as a text book, it can be used as a reference volume for graduate studies in enhanced oil recovery.