The in-situ solid/pore-water partitioning of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) was determined for an estuarine sediment profile collected from a commercial marina. Total butyltin levels exceeded sediment quality guideline values, and were 220-8750 姯kg for TBT, 150-5450 姯kg for DBT and 130-4250 姯kg for MBT. Pore-water butyltin concentrations ranged from 0.05 to 2.35 姯l for TBT, 0.07-3.25 姯l for DBT, and 0.05-0.53 姯l for MBT. The partitioning of butyltin compounds between the sediment solid-phase and pore-water was described by an organic carbon normalised distribution ratio (DOC). The observed DOC values were similar for TBT, DBT and MBT, and were 105-106 l/kg. Values for the Butyltin Degradation Index (BDI) were larger than 1 at depths greater than 10 cm below the sediment/water-column interface. This indicates that substantial TBT degradation has occurred in the sediments, and suggests that natural attenuation may be a viable sediment remediation strategy.