Solar flares which produce significant numbers of energetic protons are accompanied by optical, radio and x-ray emissions. Thus the capability for providing early warning of solar proton events (SPEs) is possible if the particle fluxes can be correlated with the electromagnetic signatures from the sun. We have continued to develop and refine the correlations between the proton fluxes in the SPE's and their electromagnetic emissions. Data from over most of solar cycle 21 and the early portion of cycle 22 have been used to extend our data base and improve the correlations between peak proton fluxes and the x-ray fluences which arrive at the earth earlier than the protons. A simple relationship has been derived between the probability of occurrence of an SPE and the observed x-ray fluence. We used a consistent data base to compare NOAA-supplied Geostationary Operational Environmental Satellite data with published Solar Maximum Mission (SMM) data sets to determine the correlation of x-rays with the ejected protons as a function of x-ray energy. The peak proton flux is best correlated with the 1-8 Å energy band fluence. The correlation coefficient between the number of protons observed and the x-ray fluence decreases slightly as a function of energy. Significant improvement in the correlation is obtained by using a sum of power laws that employs the fluence in both the 1-8Å and 5-4 Å energy channels. Incorporating the flare position as a parameter also improves the correlation between the x-ray fluence and the peak fluxes predicted.