ABSTRACT A new mechanistic drilling model for PDC bits was presented. The model was fully explicit with physical meanings given for all constants and functions. The response of the drilling model to weight-on-bit and cutters removal and the stability of constants were tested using some field and laboratory data. The preliminary results were encouraging. The concept of maximum bit performance (MBP) curve was introduced. The curves represented the maximum values of the average drilling rates for various pre-assumed footage values. In contrast to elaborate drilling models, the MBP curves are a single, comprehensive correlation representing drilling bit behavior in a formation. For calculating purposes the curves were normalized and thus they became insensitive to drillability change vs. depth as well as formation abrasiveness. The curves were plotted and analyzed for both rockbits and PDC bits. The simple method for using the MBP curves for drilling optimization was presented. A new method for preparing a multi-bit drilling program, the dynamic drilling strategy, was developed. The dynamic drilling strategy provided the best combination of PDC bit runs to achieve the minimum drilling cost for a long borehole interval. The method was numerically compared to the conventional drilling optimization and to field practices. Considerable savings of 30% and 300% respectively were estimated.