Abstract : Coronal active regions, the sites of energetic solar flares, have temperatures higher than 10 K and emit strongly in the X-ray region of the spectrum. In this report X-ray emission line-ratio diagnostics for electron density and temperature are applied to over 100 spectra of nonflaring active regions taken by the SOLEX B spectrometer aboard the U.S. Department of Defense Space Test Program's P78-1 Satellite from March to November 1979. The purpose is to draw general conclusions from analysis of the spectra of a large variety of regions. In the course of the study, we were also able to evaluate existing theoretical calculations of the helium-like ion line ratios. A number of them can now be rejected as inconsistent with the data. Future work may modify the conclusions of the study, but not significantly.