Mapping of the amplification region and full characterization of a dye laser amplifier by means of a photoacoustic technique are presented. The acoustic signals generated in the pumped medium as a consequence of nonradiative transitions are gain dependent. We use the ratio between the acoustic signal measured when the oscillator beam passes through the amplifier, to the acoustic signal when it is blocked, as a figure of merit of an amplifier stage. By using the oscillator beam as a spatial probe of the amplifier gain region, it is possible to map the optically inverted medium, assigning a photoacoustic ratio to each point of the medium. ©1996 American Institute of Physics.