Marine and estuarine sediments collected from San Diego Bay, Norfolk Harbor, Honolulu Harbor, and Pearl Harbor were analyzed for grain size distribution, clay mineralogy, percent organic carbon, and concentration of organotin toxins originating from antifouling paints. Adsorption and desorption experiments were performed on each of the sediment samples to determine variables controlling tributyltin (TBT) partitioning. Adsorption and desorption occurred rapidly and equilibrium appeared to be established within 24 hours. If sufficient binding sites were available, TBT partition coefficient values ranging from 1000 to 5000 (ug/kg per ug/l) were obtained (in agreement with literature values). For a 118 ppt TBT water concentration, 100 ng/g TBT is an approximate equilibrium sediment concentration. This value was not reached for samples without an adequate amount of available binding sites. This data will aid in the determination of the potential for bioavailability of TBT in benthic regions of waterways insulted by organotin toxins. In San Diego Bay sediments, available sites were frequently limited, thus adsorption and desorption depended directly upon the grain size distribution, clay mineralogy, and percent organic carbon of each sediment sample. Adsorption and desorption behavior of Honolulu Harbor sediments also depended upon percent organic carbon and grain size distribution, although more samples are needed to verify this. Norfolk Harbor sediments depended, at least in part, upon percent organic carbon, grain size distribution, and clay mineralogy. A few of the sediments reached the equilibrium TBT value of 100 ng/g upon exposure to a 118 ppt TBT water concentration. Pearl Harbor sediments contain a considerably higher percentage of organic matter than sediments from the other regions studied. Most of the Pearl Harbor sediments reached the 100 ng/g TBT concentration and all resulted in partition coefficients between 1000 and 5000 (ug/kg per ug/l) during the adsorption experiment.