This review presents recommendations for fluid needs and hydration assessment for recreational activity. Fluid needs are based on sweat losses, dependent on intensity and duration of the activity, and will vary among individuals. Prolonged aerobic activity is adversely influenced by dehydration, and heat exposure will magnify this effect. Fluid needs predicted for running 5–42 km at recreational paces show that fluid losses are <2% body mass; thus, aggressive fluid replacement may not be necessary. Competitive paces result in greater fluid losses and greater fluid needs. Fluid needs for recreational activity may be low; however, carbohydrate consumption (sport drinks, gels, bars) can benefit high-intensity (≤1 h) and less-intense, long-duration activity (≥1 h). Spot measures of urine color or urine-specific gravity to assess hydration status have limitations. First morning urine concentration and body mass with gross thirst perception can be simple ways to assess hydration status.