Dissolved organic matter (DOM) is a major vehicle for the translocation and loss of N and P from forest ecosystems. The chemical properties of DOM and its interactions with soil surfaces are crucial in determining the mobility of these organic nutrients. We fractionated DOM from throughfall; all soil horizons (Ultisols and Inceptisols), and stream water from an Appalachian mountain forest ecosystem into hydrophobic or hydrophilic acids, neutrals, and bases. \Ve analyzed each fraction for dissolved organic C (DOC), N (DON), and P (DOP). Most of the DOC was in the acid fractions, with the humic fractions (hydrophobic acids and phenols) comprising 35 to 57% of the DOC in all samples except summer throughfall. Concentrations of all fractions declined with depth in the soil. As a percent of total DOC, the humics declined with depth, whereas the hydrophilic neutrals increased. Bases, which we expected to contain cationic amino groups, were < 2.5% of the DOC. Instead, most DON was in the humic. hydrophilic acid, and hydrophilic neutral fractions. Most DOP occurred in the hydrophilic acid, humic, and hydrophilic neutral fractions. The functional groups in which N and P occur had little influence on the behavior of most of the DOM as a whole since: (i) cationic DOM was such a minor component, and (ii) P was simply too rare to influence the anionic behavior of many molecules. Nevertheless, for those molecules in which P did occur, P may have influenced their behavior since a large percentage of the DOP was in the hydrophilic acid (i.e., anionic) fraction. The carboxylic and phenolic functional groups, or in some cases the neutrality, of the DOM molecules appeared to be much more important than N-containing groups in influencing the behavior of the N carried passively by the DOM. D ISSOLVED ORGANIC MATTER plays an important role in interrestrial and stream ecosystems because it: (i) is a major mode of export of N and P in many ecosystems that are not experiencing severe erosion (Sollins and McCorison, 1981); (ii) plays a major role in determining the balance of soil N and P over the time of soil development; (iii) affects soil structure, e.g., resulting in a deeper redistribution of soil organic matter and the coating of clay particles with organic matter, (iv) is the principal vehicle for movement of Al and Fe in soil; and (v) provides a potential source of carbon for microbial growth (Meyer et al., 1987). Characterization of DOM in soil and stream water is very difficult because it consists of a myriad of compounds, none of which is present in large proportions. Four general approaches have been used to characterize DOM: (i) cataloging individual compounds; (ii) analyzing for broad biochemical classes of compounds such as proteins, free amino acids, monosaccharides, pplysaccharides, lipids, pplyphenols, and tannins; (iii) dividing into molecular-size classes; and (iv) compre