The intensity of Si IV lambda1397, O IV) lambda1406, N IV) lambda1488, C IV lambda1549, and O III) lambda1663 diffuse line emission recently detected toward the north galactic pole is compared to the predictions of optically thin, hot plasma emission models. Within experimental and theoretical uncertainties, compatibility between observations and theory can be achieved with an emitting gas of standard cosmic abundances in steady state ionization equilibrium at a temperature between 10/sup 5.2/ and 10/sup 5.3/ K and with an emission measure between 0.4 and 0.05 cm/sup -6/ pc. If the emitting plasma is in pressure equilibrium with the cooler phases of the interstellar medium, the physical length of the emitting region must be > or =160 pc for a gas filling factor of unity and the electron density is in the range 2.5 x 10/sup -3/ < or =n/sub e/< or = 2.5 x 10/sup -2/. This plasma may be a new, cooler, as yet unobserved component of the interstellar medium, or it could be the same gas that is responsible for the observed EUV/soft X-ray background at approx.100 eV and the O VI line absorption. These results also indicate that the galactic halo gas at 10/sup 4.9/ Kmore » cannot be the source of the observed far-UV diffuse line emission.« less