The expansion of the creep database for commercial Ni-base single crystal superalloys has been started at National Institute for Materials Science (NIMS). Presented in this report are, PWA1480 and PWA1484, a 1st generation and a 2nd generation single crystal superalloy respectively, which were developed by Pratt & Whitney, one of the largest aircraft engine manufacturers in the world. In this investigation, samples were heat treated in accordance with the literature on the alloy development, and creep tests were carried out at 800°C-735 MPa, 900°C-392 MPa, 1000°C-245 MPa, 1100°C-137 MPa, and 1150°C-137 MPa. Microstructural observations were carried out prior to and after the creep tests. PWA1484 was confirmed to have longer creep rupture lives than PWA1480 under all creep test conditions. However, at low temperature-high stress conditions, e.g. 800°C-735 MPa, large elongations were observed in PWA1484 during the primary creep stage, thus PWA1480 was found to be superior with respect to the time to 1% creep deformation. Furthermore, after the creep test at 1100°C-137 MPa, TCP phase precipitates of a plate-like morphology were observed in the microstructure of PWA1484. For the application of this alloy in components with a long expected service life, careful examinations will be required because of the TCP phase precipitation that leads to a decrease in strength.