A high-pressure DRIFT chamber for low temperature NO adsorption was newly constructed, and used to probe surface sites of the Ni-Mo-S phase on NiMo/Al2O3 catalysts sulfided at high-pressure (1.1 MPa, 673 K). A sharp IR band was evolved at 1,765 cm(-1) after NO adsorption at 186-199 K, whereas this band was not observed after NO adsorption at ambient temperature. The band at 1,765 cm(-1) was observed neither in the spectra of Mo/Al2O3, Ni/Al2O3 nor their physical mixture even after NO adsorption at 186-199 K, suggesting that this band results from adsorption of nitrosyl species on the Ni-Mo-S phase.