The overall behavior of drillstrings is complex. Dynamic behavior is the combination of the effects of axial, tortional and lateral modes of vibration. Well bore confinement offers the greatest challenge in predicting drillstring behavior. Solutions to the overall dynamic behavior of drillstrings are possible through finite element techniques. However, much can be learned through mathematical models of the various modes (axial, tortion, lateral) of motion. Coupling these analyses with measurements of downhole parameters while drilling provides much information for the design and control of drillstrings.