The specific surface area (SSA) of delustered undrawn and drawn high-speed spun PET fibers hydrolyzed in aqueous NaOH was measured using three methods : (1) geometric, based on fiber diameter; (2) gas adsorption using N-2 and the BET equation; and (3) adsorption of a nonionic surfactant. Increasing the spinning speed had little effect on the SSA of the untreated fibers, while drawing resulted in considerably larger SSA. For the hydrolyzed fibers, both adsorption methods resulted in larger SSAs than that predicted geometrically due to surface pitting. After hydrolysis, the higher spinning speed resulted in a greater increase in SSA over the untreated sample, whereas the increase in SSA was less for the drawn fibers compared to the undrawn. The kinetics of hydrolysis are also discussed.