The chromospheric h and k emission cores of the G dwarfs and subdwarfs Beta Hyi (14), Zeta Tuc (5), Delta Pav (5), and Tau Cet (5) have been monitored over a period of four years using the IUE satellite long wavelength camera. A detailed statistical examination of the data has shown that no variation in h and k fluxes of less than 15 percent could have been detected by means of this technique. This limit applies, even after removing the effects of saturation, variable gain, and scattered light between echelle orders, for any astrophysical use of comparable IUE data. No flux excursions larger than this value were detected in any of the objects presently considered.