Over the last few years, significant research has been undertaken to understand the production of odors from biosolids cake, and also to understand the factors which impact odors and finally to develop methods to reduce odors. The research reviewed in this paper shows that most odor is related to volatile organic sulfur compounds (VSCs), especially methyl mercaptan and dimethyl sulfide. These compounds are produced by the microbial degradation of protein in the cake. Greater amounts of protein have been shown to increase odorant production. Therefore, factors which will increase the bioavailable cake protein content will also increase the production of VSCs. Factors that were studied which impact bioavailable protein and increase odors include shear associated with high solids centrifuges and higher polymer dosages. Greater SRTs during digestion reduced protein content and odorant production. In developing strategies to control VSC production, the focus should be on reducing bioavailable protein.