Anaerobic ammonium oxidation (Anammox), a process ideally suited for the treatment of nitrogen-rich wastewater streams, is a promising novel biological nitrogen elimination process with attractive application prospects. However, the Anammox process is inhibited by many factors, which prevent improvements on the process as well as the application of the Anammox process. A variety of inhibitory substances, such as substrates (ammonia and nitrite), organic matter (nontoxic organic matter and toxic organic matter), salts, heavy metals, phosphate and sulfide, are commonly present in the practical applications. We conducted a detailed review of previous researches on the inhibition of Anammox processes. As a result of differences in operating conditions, experimental methods, physical structures of sludge (flocculent sludge, biofilm or granular sludge) and microbial populations involved, the effect of inhibitors varies widely. Temperature and pH adjustments, dissolved oxygen and oxidation-reduction potential controls, substrate concentration and load controls, sludge acclimatization and addition of auxiliary agents can significantly improve the performance of Anammox process under inhibitory conditions. (C) 2012 Elsevier B.V. All rights reserved.