Methods for determining an effective resonance integral from available resonance parameter data are examined and applied to lumped systems where the absorber is U238. Agreement with experiment is satisfactory in view of an uncertainty of about 10% introduced by probable errors of the parameter data. The empirical formula is expected to represent the geometric behavior of I better than other two-parameter formulas when applied to a variety of fuel element compositions. For uranium metal the formula is virtually indistinguishable from the formula of Gurevich and Pomeranchouk: Quantitative results describing the temperature and energy dependence of resonance captures are also given.