This paper reviews research and development on the causes, consequences and methods of controlling septicity in sewers. It draws on information given in 57 published papers on the subject. Explanations are given on the deviation of equations used to predict critical conditions in sewers and rising mains. The consequences of septicity, including toxicity, corrosion and odour nuisance, are described and discussed. Prevention is always recommended over cure, but where this cannot be achieved the methods of controlling septicity generally rely on maintaining an adequate supply of oxygen (dissolved or chemically available) to oxidize previously formed sulphide. Other options to cure the effects of septicity include minimizing the emission of hydrogen sulphide into the atmosphere, deodorizing vented air, and the use of protective coatings or corrosion-resistant pipes.