The coupled partial differential equations used to describe the behavior of impurity ions in magnetically confined controlled fusion plasmas require numerical solution for cases of practical interest. Computer codes developed for impurity modeling at the Princeton Plasma Physics Laboratory are used as examples of the types of codes employed for this purpose. These codes solve for the density of ions in each charge state of the impurity and their associated radiation rates using atomic physics appropriate for these low-density high-temperature plasmas. The simpler codes solve local equations in zero spatial dimensions while more complex cases require codes that explicitly include transport of the impurity ions simultaneously with the atomic processes of ionization and recombination. Typical applications are discussed and computational results are presented for selected cases of interest.