A nickel-base superalloy that is useful for making single crystal castings exhibiting outstanding stress-rupture properties, creep-rupture properties, and an increased tolerance for grain defects contains, in percentages by weight, from about 4.7% to about 4.9% chromium, (Cr), from about 9% to about 10% cobalt (Co), from about 0.6% to about 0.8% molybdenum (Mo), from about 8.4% to about 8.8% tungsten (W), from about 4.3% to about 4.8% tantalum (Ta), from about 0.6% to about 0.8% titanium (Ti), from about 5.6% to about 5.8% aluminum (Al), from about 2.8% to about 3.1% rhenium (Re), from about 1.1% to about 1.5% hafnium (Hf), from about 0.06% to about 0.08% carbon (C), from about 0.012% to about 0.020% boron (B), from about 0.004% to about 0.010% zirconium (Zr), the balance being nickel and incidental impurities. The nickel-base superalloy provides improved casting yield and reduce component cost due to a reduction in rejectable grain defects as compared with conventional directionally solidified casting alloys and conventional single crystal alloys.