The variation of porosity in quartzose sandstones is calculated as a function of depth, temperature gradient, burial rate, stylolite frequency, and hydrocarbon saturation. Calculations were performed by considering the effects of both mechanical compaction and chemical compaction/cementation. This latter process dominates at temperatures greater than approximately 90°C and is due to quartz redistribution within the sandstone. Quartz redistribution stems from clay-induced quartz dissolution at stylolite interfaces, coupled with diffusional transport of aqueous silica into the intersty-lolite sandstone and precipitation on quartz surfaces as cement. Many model parameters are obtained from theoretical calculations or laboratory measurements, and few basin-dependent parameters are required to make porosity predictions. A set of porosity predictions is presented in porosity/depth figures. Close correspondence between computed results and measured porosities in cores from a variety of sedimentary basins demonstrates the accuracy of the predictions.