Several common materials and methods used to collect interstitial water (IW) were evaluated to determine their effect on the accuracy and precision of measured concentrations of selected organic compounds and metals. The concentration of pollutants in dosed seawater before and after exposure to stainless steel and Teflon centrifuge tubes, glass fiber and Nuclepore filters, cellulose dialysis membranes and fritted glass tubes were compared. Exposure to most hardware materials did not significantly affect the concentration of four metals (Cd, Cr, Cu, Pb) but there was significant loss (up to 79 percent) of two organic compounds (fluoranthene, p,p'-DDE) to almost all the hardware materials tested. Of five commonly used IW collection methods (centrifuging, centrifugal drainage or basal cup, squeezing, vacuum filtration and dialysis) investigated, the centrifuge method was judged the most accurate and precise for polycyclic aromatic hydrocarbons and PCBs. All IW collection methods tested showed high variability for the metals. As a result, with one exception (Cu), there was no significant difference detected in the accuracy of the methods for metals.