Scientists and engineers specialized in geochemistry, chemistry, biology, and ecology of natural waters have collectively contributed thousands of published works dealing with natural organic matter (NOM). That body of scientific information is dispersed across a wide range of disciplinary journals and books, and it ranges in quality from the mundane to the exceptional. This review includes quantitative estimates of the global riverine transport of NOM from the continents to the oceans and the corresponding average concentration of total organic carbon in rivers, methods of isolation and characterization of NOM from inland waters, and simple statistical summaries of the most commonly reported chemical properties of NOM. The chemical properties of NOM are compared and contrasted with those of the major components of biomass to highlight the most distinctive traits of NOM – its high degree of oxidation, its high level of unsaturation, and its high concentration of carboxylic acid functional groups. An integrated analysis of the major chemical properties of NOM, based on the mean and median results of the statistical summaries, is used to demonstrate consistency (or the lack thereof) among reported properties of NOM.