Two spectroradiometers, one based on a conventional prism monochromator and the other on a system employing narrow band pass interference filters, have been set up and independently used in the determination of the spectral irradiances of a number of sources over the wavelength range from 0.25 micro to 2.5 micro. Basically, the method of calibration for each system consists of comparing the spectral irradiance of the source under investigation with that of an NBS standard of spectral irradiance. The results obtained wit h each system on a number of continuous sources agree to about 1% whereas the differences in the spectral irradiances obtained with the two setups on a number of line sources range up to several percent.