This review examines the influence of dehydration on muscular strength and endurance and on single and repeated anaerobic sprint bouts. Describing hydration effects on anaerobic performance is difficult because various exercise modes are dominated by anaerobic energy pathways, but still contain inherent physiological differences. The critical level of water deficit ([approximately] 3-4%; mode dependent) affecting anaerobic performance is larger than the deficit ([approximately] 2%) impairing endurance performance. A critical performance-duration component (greater than 30 s) may also exist. Moderate dehydration ([approximately] 3% body weight; precise threshold depends on work/recovery ratio) impairs repeated anaerobic bouts, which place an increased demand on aerobic metabolism. Interactions between dehydration level, dehydration mode, testing mode, performance duration, and work/recovery ratio during repeated bouts make the dehydration threshold influencing anaerobic performance mode dependent. (Contains 3 tables.)