Soil water distribution coefficients (K d ) for methyl tert-butyl ether (MTBE) and its primary biodegradation intermediate tert-butyl alcohol (TBA) were determined for seven hyporheic zone soils ranging from 1 to 7% in organic carbon. Samples were collected in the area of the Spring Creek hyporheic zone in Ronan, Montana. Values for K d ranged from 1.5 to 8.7 L kg−1 for MTBE and from 0.15 to 0.41 L kg−1 for TBA, and were highly correlated to the organic carbon content of the solids. However, for TBA the use of non-linear K F values is more appropriate based on the results obtained, and the value of K OC is calculated based on linear K d transformation of the data. Distribution coefficients normalized to the fraction of organic carbon (log K OC ) for MTBE and TBA were determined to be 2.13 ± 0.060 and 0.762 ± 0.088, respectively.