The electrical characteristics of epitaxial germanium tunnel diodes prepared by a solution regrowth technique are presented. The conduction processes occurring in these diodes are described in terms of Kane's theory of band-to-band tunneling at low forward bias, and by Chynoweth's model of tunneling by means of localized states in the forbidden region for biases in the excess current region. In the direct tunneling region, the exponential dependence of the tunneling probability on carrier concentration has been qualitatively verified, and the peak tunneling voltage is shown to be dependent on the penetration of the Fermi level in the n- and p-type regions. The junction capacitance in the valley region closely follows the theoretical values of the capacitance of abrupt p- n junctions. In the indirect tunneling region, the exponential dependence of excess current density on junction depletion layer width is shown to be in agreement with Chynoweth's model. The effects of ambient temperature and nuclear radiation on the electrical characteristics of these diodes are presented. The experimental results are in good agreement with the theories of Kane and Chynoweth.