This study is the first report on the extraction of poorly soluble drug molecules such as nifedipine, niclosamide, and furosemide from the organic phase to the aqueous phase by water-soluble p-phosphonate calix[n]arene receptors via a liquid-liquid phase extraction process. These water-soluble calixarene derivatives were easily obtained from the reaction between their corresponding chloromethylated derivatives and trimethyl phosphite. From the liquid-liquid phase extraction studies, it was observed that the size of the p-phosphonate calix[n]arenes changed the extraction percentage of selected drug molecules. © 2011 American Chemical Society.