The design of the inlet system has been regarded as a major factor in the internal homogeneity of the casting. Being designed correctly, the system should ensure the proper and continuous filling of the mold cavity. Continuous filling of the cavity gives the initial prerequisite for internal soundness and homogeneity of the casting reflected in its quality and mechanical properties. The paper deals with the design of the inlet system for a particular type of the casting, its optimization using computer simulation as well as evaluation of the real results measured on the casting physical models.