Three sequential extraction schemes in sediments, namely SEDEX scheme (Ruttenberg, 1992), Modified SEDEX scheme (Vink et al., 1997) and Agemian scheme (Agemian, 1997) were employed in the study of three, less than 125 µm fraction of the sediment samples. These sample were collected from Chao Phraya, Mae Klong and Bang Pakong Estuaries. The objective of this study is to compare phosphorus partitioning results in sediment by the three extraction schemes. In addition, the samples were analyzed for total phosphorus contents by X-ray fluorescence spectroscopy (XRF), ignition methods (Aspila et al., 1976; Vink et al., 1997; Agemian, 1997) and total digestion method (HF-HCIO₄-HNO₃). The total phosphorus contents were used in evaluating the accuracy of the extraction schemes by comparing these values with the sum of all phosphorus fractions. All schemes show different and incomparable results. However, in terms of accuracy, the Agemian scheme shows the most promising results with higher accuracy and precision than those by Ruttenberg (1992)'s and Vink et al. (1997)'s. Eventhough three schemes are incomparable quantitatively but qualitatively all three show the same trend of having Fe-P as the most dominant fraction in all samples. Other fractions show different relative dominant in different samples, which may be caused by the geological conditions and weathering processes in the watersheds and human activities.