In recent years, computer simulations gained an increased role in the design, development, optimization, and calibration of the valve train systems. With the development of non-conventional systems and actuation mechanisms, computer modeling became even more important. Part I of this article presents an overview of the current modeling and simulation methods of conventional valve trains at component and system level. First, the modeling of the valve train kinematics, including cam shape design and optimization, is summarized. Mathematical modeling of the valve spring, hydraulic lash adjuster, oil aeration, bulk modulus, contact stiffness and contact damping in multibody systems are discussed. The benefits and limitations of the different modeling approaches of the valve train dynamics are pointed out. Another important aspect is the valve train tribology. Elastohydrodynamic contact modeling, lubricant film thickness prediction, lubricant rheology, starvation, and asperity contact are discussed extensively. Current prediction capabilities of friction and wear in the main tribological contacts are presented and new research directions are pointed out. Part II of this article will discuss the modeling and simulation of variable cam timing systems and variable valve actuation mechanisms. Nontraditional and conceptual solutions including mechanical, electromechanical, electrohydraulic, electromagnetic, pneumatic, piezoelectric, and magnetorheologic actuation as well as control theories will be presented.