Calculations show that high-excitation planetaries emit about the same total intensity of collisionally excited radiation in the unobserved ultraviolet part of the spectrum as in the visible. This ultraviolet radiation emanates from a central zone where the electron temperature is high due to absorption of He II Ly-α photons. Intensities of lines which one might expect to detect in the ultraviolet have been calculated using revised atomic data and a detailed model of the ionization and thermal structure of the central zone. Relative line intensities are presented for a wide range of excitation in the nebula. In particular, the absolute intensity of the C IV doublet at 1550 Å has been calculated for 4 selected planetaries.