We characterize the linear viscoelastic properties of complex fluids using a new technique, based on the measurement of surface fluctuations: surface fluctuation specular reflection (SFSR) spectroscopy. The thermally excited waves propagating on a free surface are measured through the deflection of a laser beam specularly reflected from that surface. Elastic and loss moduli of the complex fluids are inferred from the measured power spectrum density of thermal noise, with the implicit use of Kramers-Kronig relations. The technique, besides being noninvasive, provides rheological data in a large frequency range and at vanishing strains. It is therefore especially well suited for the rheological characterization of complex fluids. We present measurements of the viscoelastic modulus of supramolecular polymer solutions in a frequency range extending up to six decades. We compare the SFSR measurements with rheometric data at low and high frequencies, and show that they are in good agreement. Using supramolecular polymer solutions of different natures, exhibiting or not surface viscoelasticity, we furthermore show that SFSR provides a characterization of the bulk properties of the fluids. In addition, we discuss the accuracy of the measurements. (C) 2013 The Society of Rheology. [http://dx.doi.org/10.1122/1.4776745]