The objective of the present study is to investigate dissolved organic matter as a potential carrier of soluble organic nutrients in throughfall, steamflow, and soil water at 10, 60 and 200cm soil depth under species of natural vegetation and of agoforestry systems near Manaus/Amazonia. The analysis of dissolved organic matter can help to improve the understanding of nutrient cycles in tropical rainforest ecosystems. Because not much is known about dissolved organic matter in the inner tropics, this understanding can help to improve the efficiency of agroforestry systems which are established in the inner tropics without damaging the natural environment in an irreversible way. The investigation area is situated at the EMBRAPA-CPAA research station near Manaus/Amazonia. The average amount of precipitation is about 2101 mm per year with maxima between December and May. The natural vegetation is tropical rainforest. The soils of the area are xanthic Ferrasols (FAO-classification), characterized as strongly weathered, with low pH, high nutrient losses, and clay contents up to 80%. Throughfall, stemflow, and soil water at 10, 60 and 200cm depth were sampled in January 1999 under species of an agroforestry system (Bactris gasipaes Kunth., Theobroma grandiflorum (Willd. Ex Spreng.) K. Schum, Pueraria phaseoloides), of a secondary (Vismia spp) and of a primary forest (Oenocarpus bacaba, Eschweilera spp). This samples were analyzed for inorganic and total organic N and S contents and organic carbon. In addition, a fractionation procedure was used to separate labile hydrophilic and refractory hydrophobic (humic) compounds. The fractionated samples were analysed for nutrient and carbon contents. The mean concentrations od Dissolved Organic Carbon (DOC) fluctuated between 3.99 mg l-¹ (Puearia) and 8.32 mg l-¹ (Eschweilera) in throughfall. This agrees well with studies of different ecosystems. The concentrations of DOC were larger in steamflow than in throughfall. In both, throughfall and steamflow, DOC was mainly in the hydrophilic fraction (up to 94% of the total DOC) under all the investigated tree species. This means that DOC in the above ground biomass is mainly a product of microbial activity and of dry deposited organic matter. The mean concentrations of Dissolved Organic Nitrogen (DON) were up to 1.60 mg l-¹ under Oenocarpus bacaba and, as for DOC, agree with several other studies. The comparable low content of DON and the simultaneous dominance of the hydrophilic fraction in throughfall of Bactris gasipaes, Pueraria, and Eschweilera, and in steamflow of Bactris gasipaes and Eschweilera is opposite to their high nitrogen contents within their above ground biomass. Simultaneously the concentrations of DON in throughfall and steamflow of Theobroma grandiflorum and Oenocarpus bacaba are higher in comparison to the other investigated species, although the nitrogen contents in above ground biomass are lower. For these species there is also a dominance of the hydrophobic fraction. This means, that the release of organic nitrogen from the canopy and the stems is not primarily a process of leaching from deposited organic matter but is a product of microbiological activity. In comparison with a study of a temperate forest the mean concentrations of Dissolved Organic Sulfur (DOS) seem to be very high. In throughfall, stemflow and at the different soil depths, DOS was only detectable in the hydrophilic fraction. Probably DOS is primarily a product of microbial activity with high contents of amino compounds. The mean concentrations of DOC reached up to 12.39 mg l-¹ (Bactris gasipaes) at 10cm soil depth in agreement with other studies. While there was a decrease of organic carbon with increasing soil depth under the species of the agroforestry system, the DOC concentrations increased with increasing soil depth under the species of the agroforestry system, the DOC concentrations increased with increasing soil depth under the tree species of the primary forest. For DON, the concentration increased under all species with increasing soil depth or remained inchanged. This suggests that organic N is more mobile than DOC. DON comprised up to 90% of the total nitrogen. This opposite to studies of temperate forests, where Dissolved Organic Matter (DOM) decreases with increasing soil depth. A reason for the retention of DOM with increasing soil depth in temperate forest ecosystems is the sorption of mainly hydrophobic compounds at mineral surfaces and sesquioxides in soil. The relitively high concentrations of DOC and DON with a dominance of the hydrophobic fraction in 200cm soil depth are probably caused by a simple enrichment, or by microbial reduction of particularly organic substances. This suggests that sorption processes in the investigated soil occur mainly in the upper soil areas and probably, the investigated soil has in general a low sorption capacity with respect to DOM. Under the condition of low sorption capacity, the hydrohobic organic substance in 200cm soil depth could be the result of formed and directly accumulated lignine degradation products which are normally hydrophobic. The largest DOS concentrations occurred in the topsoil. Here, up to 80% of the total S wa organically bound. The concentrations of DOS increased strongly with soil depth. Thus, DOS was less mobile in these soils than DOC. The increase of DON and the decrease of DOS with increasing soil depth indicate that there may not be a change of the DON and DOS mobility as a result of the change of land use in the tropical rainforest ecosystems. Therefore, agroforestry systems seem to be a reasonable way to use the natural resources of tropical rainforest ecosystems without destroying them.