The preparation of two near-shore marine sediment reference materials in our laboratories, as part of the National Research Council Marine Analytical Chemistry Standards Program, involved a very large number of determinations of about 25 elements at major, minor and trace levels. A procedure which permits the simultaneous determination of 5 major constituents (Fe, Al, Ca, Mg and Na) and 9 -minor and trace elements (P, Mn, Pb, Co, Ni, V, Cu, Be and Zn) in marine sediments by inductively coupled plasma atomic emission spectrometry (ICP-AES) has been developed. Solutions are prepared by mixed acid (HNO3/HC1O4/HF) digestion of 0.5 g samples in sealed Teflon vessels at 100°C, evaporation of the residues to dryness, and redissolution in 50 ml of 1 MHC1. Calibration of the spectrometer is achieved by means of multielement standards in 1 M HC1. Accurate trace analyses in many cases require corrections for various spectroscopic interferences arising from background shifts or line overlaps. These are accomplished by making off-peak background intensity measurements and by incorporation of correction factors in the data processing software.