An interactive isoparametric contour plotting and filling program, ISOCON, is developed for use with finite element meshes using common two-dimensional triangular and quadrilateral elements. The program uses the local interpolation functions to compute the contour locations. The predictor-corrector algorithm used to compute the contour locations is derived and discussed. The color filling algorithm is also discussed. The program features are given along with a brief discussion of selected algorithms used in the program. The main feature of ISOCON lies in its portability since most plot drivers are written in FORTRAN 77. Selected contour plots are compared with output from another finite element contour plotting program. The ISOCON-generated plots produce much more realistic looking contours. Partial FORTRAN code along with a flowchart is included.