Laser osteotomy offers remarkable advantages, e.g. free cut geometry, over the conventional mechanical saw. Unlike the saw, however, the laser lacks haptic feedback during cutting. Based on ablation noise analysis, we are developing an acoustic-feedback system for laser osteotomy to obtain in situ information on the ablation within the tissue. We used a pulsed TEA CO2 laser (wavelength 9.57µm, pulse length 1µs/50ns FWHM, pulse energy 25 mJ) and piezoelectric transducers for sound detection. Various bone specimens as well as reference materials were stud- ied. For the determination of the ablation crater depth, we analyzed the time delay between the laser-induced acoustic signal from the surface of the specimen and the bottom of the ablation crater. The possibility of control- ling the cut depth in material with known acoustical properties with high precision is demonstrated. For acoustic tissue differentiation, we analyzed acoustic spectra initiated by laser pulses in different materials. The spectra show specific material-based features. This will prompt surgeons with information about the transi- tion from compact bone to other materials, e.g. soft tissue. An acoustic feedback system will eventually provide online control over the depth of the incision and ancillary recognition of the tissue exposed to the laser.