This paper describes methods to predict common mineral scales and corrosion in gas and oil fields. The calculations result from the unification of the scale prediction methods of Oddo and Tomson and the CO2 corrosion prediction methods of de Waard and Lotz (Corrosion 93, Paper No. 69). Background development of the calculations is discussed in the paper. The scale prediction algorithms accurately calculate many of the parameters needed for the corrosion estimations that were proposed in the original paper by de Waard and Lotz. By including the calculated values, more accurate corrosion estimates are obtained. The scale prediction calculations have also been updated and revised to more accurately predict mineral scale deposition. This paper includes field examples of scaling and corrosive production systems to illustrate the use of the methods. The prediction model uses produced water chemistry and production volume data, as well as, flowing wellhead temperature and pressure and bottornhole temperatures and pressures to estimate temperatures and shut-in and flowing pressures in a well to calculate the needed parameters. The model will accept a dovmhole pump and can be used with wells containing rod and electrical submersible pumps. The calculations are quite accurate and result in a scale/comosion model that can be used to develop field treatment strategies and/or assist in material selection. As is true with the de Waard and Lotz methods, the corrosion calculations predict a ‘worst case’ corrosion scenario.