The　aim　of　this　study　was　to　explore　the　relationship　between　biomechanical　properties　and　the　occurrence　of　pelvic　organ　prolapse　(POP)　through　analysis　on　biomechanical　properties　of　vaginal　tissue.　The　biopsy　specimens　were　obtained　from　43　patients　undergoing　transvaginal　hysterectomy,　who　were　assigned　into　premenopausal　POP,　postmenopausal　POP,　premenopausal　control　and　postmenopausal　control　groups.　Tissue　specimens　were　biomechanically　assessed　by　a　purpose-built　tissue　puller　system,　and　stress-strain　curves　were　digitally　recorded.　The　Young＇s　modulus,　Poisson＇s　ratio,　maximum　elongation,　maximum　fracture　of　vaginal　tissue　were　9.45±0.70,　0.43±0.01,　1.50±0.02,　0.60±0.02　in　premenopausal　POP　group;　12.10±1.10,　0.39±0.01,　1.14±0.05,　0.27±0.03　in　postmenopausal　POP　group;　6.65±1.48,　0.46±0.01,　1.68±0.11,　0.79±0.05　in　premenopausal　control　group　and　10.26±1.10,　0.42±0.01,　1.37±0.04,　0.42±0.03　in　postmenopausal　control　group.　There　was　significant　difference　in　biomechanical　properties　between　premenopausal　POP　group　and　premenopausal　control　group　(p＜0.01).　There　was　significant　difference　in　biomechanical　properties　between　postmenopausal　POP　group　and　postmenopausal　control　group　(p＜0.01).　Biomechanical　properties　in　POP　group　were　significantly　lower　than　that　in　control　group,　suggesting　that　degeneration　of　biomechanical　properties　in　pelvic　support　construction　might　lead　to　the　occurrence　of　POP.　©　International　Urogynecology　Journal　2006.