With the exception of sediment deposited close to land, organic matter in marine sediments is derived mainly from planktonic debris from the local biomass. Since planktonic material is principally composed of proteins and carbohydrates (hemicellulose), it is of interest to compare the pathway of organic decay in a marine sediment with that of a terrestrial soil where lignin and cellulose is the chief organic input.The article briefly summarizes the present state of knowledge on early diagenesis of organic matter in marine soils. Information is based on the authors studies on distribution of amino acids and sugars in marine sediments deposited under reducing and oxidizing conditions. It is concluded that diagenesis is controlled by (i) biological degradation at the sediment-water interface, (ii) organic condensations, (iii) organic-metal ion interactions, and (iv) organicmineral interactions.