Opto-acoustic spectroscopy refers to the measurement of optical absorption by a sample using acoustic methods to detect the degree to which the sample has been heated by the absorbed radiation. This technique has numerous applications, including monitoring trace contaminants in the atmosphere. It is especially useful in situations requiring the quantitation of weak absorption spectra or circumstances where a large dynamic range is required. This paper summarizes the results of recent experiments in which acoustic resonance has been used to enhance signal levels and improve detectivity. Scaling laws are given which allow the dynamic range and detectivity of this technique to be determined. Consideration is given to the use of both coherent and incoherent light sources, and comparisons are made to conven-tional techniques such as absorption spectroscopy. Finally, the application of optoacoustic spectroscopy to the measurement of collision-broadened absorption lineshapes is discussed.