We have developed a combustion analysis technique for sediments which measures the amount of O2 consumed by the reduced species. We have measured this quantity, which we call combustion oxygen demand (COD), on a carbonate-rich sediment core from the Ontong-Java Plateau in the western equatorial Pacific back to marine oxygen isotope stage 11. The precision of the COD technique is ¿6.3 μmol O2 g-1, which corresponds to ~¿0.0076% wt Corg, assuming oxidation of organic carbon dominates the signal. The COD time series is characterized by values which are about twice as high during glacials as during interglacials, the largest shift occurring from 401 μmol O2 g-1 in midstage 6 to 144 μmol O2 g-1 at 5e, and is coherent with the oxygen isotope curve of Globigerinoides sacculifer in the same core at the Milankovitch frequencies of 100 and 41 kyr. Pronounced variations in the 19--23 kyr band suggest that the climate of the western equatorial Pacific is sensitive to precessional forcing, a response not apparent from other records obtained in this region. ¿ 1998 American Geophysical Union