Low-cycle-fatigue (LCF) and fatigue-crack-growth (FCG) behaviors of a cobalt-based HAYNES 188 superalloy were studied at temperatures ranging from 816 to 982 A degrees C in laboratory air. Various tensile-hold times were imposed at the maximum strain and load in the LCF and FCG tests, respectively, to examine the high-temperature fatigue and creep-fatigue interactions. In this article, the effects of hold time and temperature on the cyclic-stress response, fatigue life, fracture mode, and crack-growth rate are discussed. Parameters based on the tensile-hysteresis energy are applied to correlate the LCF lives with and without hold time.