This article establishes a set of uniform procedures for quantitatively characterizing closed-loop gaseous helium cryopumps. Topics include a listing of technical definitions and hardware illustrations of cryopumps; safety considerations in the use of cryopumps; methods and procedures for determining the speed, ultimate pressure, capacity, cool-down time, impulsive gas load tolerance, regeneration time, thermal radiation tolerance, and maximum throughput tolerance of cryopumps; and, a method of measuring the vibration characteristics of cryopumps.