We have measured the cross section for production of metastable (28) atoms by the process of dissociative excitation of molecular deuterium by electron impact;. The measurement includes the quantitative evaluation of detection efficiency, density, and geometrical factors necessary to establish an absolute scale on a purely experimental basis. The method depends on the application of an rf field at the Lamb-shift frequency (1059 MHz) to quench the metastables at the point of excitation. The radiation induced by the applied field is isotropic so that the absolute cross section depends on a simple solid-angle correction. The cross sections at 23. 8 and 39.1 eV are 2. 97 x 10-~a nd 3.40 x 10-~8 cm2, respectively, vrith a probable error estimated to be + 14%. The energy dependence of the cross section eras also measured from threshold to 500 eV.