The gas holdup behavior in a nylon fiber suspension with various fiber lengths (L = 2, 3, and 6 mm) is investigated. Experiments are performed over a range of superficial gas velocities (U-g less than or equal to 18 cm/s) and a range of fiber mass fractions (0 less than or equal to C less than or equal to 1.8%) in a 15.24-cm-diameter semibatch bubble column. Day-to-day variations in the gas holdup create difficulties in interpreting the effect of the fiber mass fraction. These variations are attributed primarily to nylon fiber surface additives leaching into the suspension water and loss of hydrophobicity in a prolonged water environment. As an alternative, the gas holdup in rayon fiber suspensions is highly reproducible.