The range of NBS radiometric calibration services has been extended into the far ultraviolet region of the spectrum where a dc high power hydrogen wall-stabilized arc is used as a primary standard of spectral radiance. A capability in the range 130 nm to 360 nm (overlapping conventional tungsten strip lamp radiometry) is presently available with estimated uncertainties between 5 and 10 percent depending upon wavelength. The status of radiometric source standards in the far ultraviolet is briefly reviewed and the hydrogen arc and NBS calibration facility are described in detail. The use of commercially available mercury Krefft-Rossler lamps and deuterium arc lamps as transfer or secondary standards is discussed and the spectra of these lamps calibrated with the hydrogen arc standard are presented.