Three dimensional FEM analysis has some problems in practical application because of complecated element division and large number of node and element data involved. It still should be payed attention to save computing time by considering proper element idealization and minimizing the number of nodal points, though some specific program such as automatic data input program has already been prepared for actual computation. This paper discusses practical application of three-dimensional finite elements in the analysis of field problems. Simple tetrahedral elements may be convenient if they are assembled as eight-cornered brick elements. Average element stiffness matrix is employed in this case, dividing brick elements in two different ways. Isoparametric triangular prizm element is also introduced here as another useful element and the process of the formulation of element stiffness matrix is presented
