Time‐resolved detection of the surface acoustic waves (SAW) generated upon relaxation of energy optically absorbed in surface films has been used to measure surface absorption spectra and laser‐induced desorption cross sections. This new background‐free spectroscopic technique is shown to be highly sensitive to the details of the film/substrate bonding. Minimum detectable molecular surface densities of 2×1011cm−2over an area of 10−3cm2have been demonstrated for rhodamine‐590 dye on a crystal quartz substrate using a pulsed laser source and an edge‐bonded SAW detector.