Molecular recognition in water based on ion-pairing is hampered by competition from the solvent. Wehave reported that synthetic receptor 1 recognizes inositoltrisphosphate (IP3) with a binding constant of 108 M-1 inmethanol. In this paper, instead of working in methanol,we report that the surfactant Triton-X 100 also yields a largeabsorbance or fluorescence change and a binding constanton the order of 106 M-1.