Recent studies have shown that there are well defined average abundances of heavy (Z≳2) solar energetic particles (SEPs), with variations in the acceleration and propagation producing a systematic flareâ€toâ€flare fractionation that depends on the charge per unit mass of the ion. Correcting the average SEP abundances for the fractionation yields SEPâ€derived coronal abundances for 20 elements. Higher resolution SEP studies have also provided isotopic abundances for 5 elements. SEPâ€derived abundances indicate that elements with high first ionization potentials (≳10 eV) are depleted in the corona relative to the photosphere and provide new information on the solar abundance of C and ^(22)Ne. Future SEP observations offer the prospect of a significant reduction of the uncertainties in solar elemental and isotopic abundances. ; © 1989 American Institute of Physics. Published online 01 March 1989. I appreciate T. L. Garrard's help in preparing this manuscript. This work was supported in part by NASA under contract NAS7-918 and grants NGR 05-002-160 and NAG5-722. ; Published - 1988-10.pdf