Information storage medium, and recording/reproducing method and apparatus

An information storage medium includes: a user data area for recording user data; a spare area including spare blocks each for replacing a defective block occurring in the user data area; and a defect management area in which information about the defective block occurring in the user data area is recorded, wherein the spare blocks of the spare area include usable spare blocks with replacement blocks existing in forward parts of the usable spare blocks in a usage order, and usable spare blocks without replacement blocks existing in forward parts of the usable spare blocks in the usage order, wherein a next available position pointer of the spare area is recorded in the defect management area,; and the next available position pointer of the spare area indicates a first usable spare block from among the usable spare blocks without the replacement blocks existing in the forward parts of the usable spare blocks in the usage order.