A combined gas chromatographic-mass spectrometric technique was used to identify and quantitate the occurrence of myo-, chiro-, and scyllo-inositol in marine sediments. The most abundant isomer was myo-inositol. These inositols were found in all the organic-rich sediment samples examined, and the amount of inositol decreased steadily with the age of the sample. A small fraction of the inositols occurred as hexaphosphate esters.