Rhizon samplers were originally designed as micro-tensiometers for soil science forseepage water sampling in the unsaturated zone some ten years ago. We have introducedthese samplers for the use in marine sediments and in saturated groundwaterenvironments for direct pore water sampling.Rhizons consist of a small microporous polymer tube (2.5mm diameter) supported bya stabilizing wire that is connected to a PVC-tube and a standard luer-lock connector.By attaching vacuum to this connector (syringe, vacuumtube or peristaltic pump)small volumes of pore water samples may be extracted from sediments without furthermaintenance. As a side effect of the 0.1 micron pore width of the polymer tube,the samples are automatically filtered. We successfully used these samplers for highresolution sampling from closed sediment cores. The Rhizons were inserted through3mm holes in the liner walls. By this method very high resolution pore water profilesamples may be taken without disturbance of the sediment structure. Since samplesare collected in directly attached syringes or vacuumtubes, contact with ambient oxygenis avoided for anoxic environments, thus eliminating both, the need for glove boxsampling and eliminating the need for cumbersome pressure filtration. Recently otherRhizon models with carbon fibre support and microporous tube diameters down to1mm have been presented.