Depuration is a process in which shellfish are held in a clean water environment for a time sufficient to permit them to free themselves of transient pollutional microorganisms through normal biological processes. The objectives of this report are to present the principles upon which the satisfactory depuration of shellfish depend and to establish guidelines for properly accomplishing a depuration program. The principal factors include the quantity and quality of sea water, time for depuration, construction of the plant, location and laboratory control. Plant operation guidelines are also presented.