Abstract <p>Ozone formation has been detected during ultrasonic sonolysis of air-saturated concentrated sulfuric acid. The formation of ozone is confirmed by absorption spectra (λ_max = 258 nm), as well as by a chemiluminescent test: luminescence flashes upon addition of finely divided sulfur and UO₂SO₄ solution to ultrasound-treated samples. The spectrum of multicluster sonoluminescence of sulfuric acid was found to contain a sonochemiluminescent component in the region of longer than 600 nm along with the multiemitter sonoluminescence band at 250–550 nm of the acid itself. These are luminescence bands in the red and IR spectral regions, the emitters of which are singlet oxygen and its dimol, products of chemiluminescent decomposition of ozone. A mechanism for ozone formation during sonolysis of aerated sulfuric acid is proposed by analogy with radiolysis.</p>