Discoveries since 1990 of several new and surprising forms of anaerobic metabolism promise to revise and expand our understanding of anaerobic metabolism and biogeochemistry in wetland ecosystems. For the most part, research on these processes has not been undertaken in vegetated soils or sediments. My objective is to provide an overview of recent advances in anaerobic metabolism of interest to wetland biogeochemists. Several alternative pathways for producing N₂ that do not involve the classical enzyme systems of denitrification have recently been either confirmed or investigated in detail. The contribution of these processes to N₂ production is largely unknown, but limited evidence suggests they may be quantitatively important. The most intriguing of these is anammox or anaerobic ammonium oxidation, a reaction that is now known only in marine systems. Anammox consumes 1 mole of NH₄⁺ (oxidant) and 1 mole of NO₃^- (reductant) yielding 1 mole of N₂. Anammox bacteria have unusual features such as novel lipids and internal compartmentalization similar to Eukaryotes.