Effects of focused Ar+laser irradiation on YBa2Cu3Oxin air, N2, and O2ambients were studied with a Raman microprobe. Drastic changes in the Cu‐O stretching mode (Ag) in our Raman spectra recorded in air ambient indicate an orthorhombic to tetragonal phase transformation in the YBa2Cu3Oxsample. Laser irradiation of the sample in oxygen ambient shows a reversed behavior compared to that in air. When irradiated in nitrogen ambient, it shows additional Raman lines compared wot the spectra for the starting material. This may be due to formation of BaCuO2and O(4) vacancies. The reversibility of oxygen exchange in nitrogen and oxygen ambient was also studied. The observed effects in the Raman spectra were interpreted as the chemically induced oxygen desorption and absorption assisted by Ar+laser irradiation.