BACKGROUND Considerable problems occur in transscleral laser cyclophotocoagulation concerning energy dosage. We investigated the feasibility of localizing the ciliary body by the detection of thermoelastic pressure transients and of supervising on-line the degree of tissue damage during treatment. METHODS We used a specially designed handpiece to apply short pulsed laser radiation with low energy levels to enucleated bulbs of rabbits. With an adjusted pressure transducer we examined acoustical transients generated in the area of absorption of the ciliary muscle or the pigmented epithelial layer and measured axial resolution of the method at various distances to the corneoscleral limbus. RESULTS We detected acoustic transients that allowed rough localization of the target area. A marked change in signal was recorded with increasing level of ciliary destruction. CONCLUSIONS This procedure can serve as an essential tool in the on-line supervision of the coagulation process. The laser parameters can thus be adjusted optimally to the progress of the treatment.