The interactions of dipeptides with Triton X-100 in aqueous solution have been investigated by means of density, fluorescence spectroscopy and UV-vis spectroscopy. The standard partial molar volume (V-2(o),phi), standard partial molar volume of transfer for dipeptide from water to aqueous Triton X-100 solution (Delta V-t(o)) and partial molar expansibility (E-phi(o)) have been calculated from density data. Fluorescence spectroscopy was used to estimate the critical micellar concentration (c(cmc)) and micelle aggregation number of Triton X-100 in aqueous dipeptide solutions. Effects of temperature and hydrocarbon chain length of dipeptides on the volumetric properties of dipeptide and critical micelle concentration (ccmc) of Triton X-100 were examined. The pyrene fluorescence spectra were also used to study the change of micropolarity produced by the interactions of Triton X-100 with dipeptides. From the results of UV-vis absorption spectra, the binding constant between dipeptide and Triton X-100 above the ccmc was determined. The results have been interpreted in terms of solute-solvent interactions and structural changes in the mixed solutions. (C) 2013 Elsevier Ltd. All rights reserved.