PURPOSE: To analyse the obstacles to prevent the reduction for dislocation of the metacarpophalangeal (MP) joints of the hand and evaluate the relationship between the sex and dislocation type in closed reduction case. MATERIALS AND METHODS: Total 27 cases of MP joint dislocation of the hand (11 cases of thumb, and 14 index and 2 little finger) were reviewed retrospectively. The anatomical structures to prevent the reduction were confirmed at operation and the cases which were reduced immediately were also analysed for their ages and differences of damaged structures, and finally their complications or outcome were reviewed for average 7 months after reduction. RESULTS: In 11 cases of thumb MP joint dislocations, the complex dorsal dislocations in which the protruded metacarpal neck was caught by buttonhole of torn anterior joint capsule, volar plate and FPB were reduced by open method in 8 cases, and closed reduction was done in 2 cases but one old case required arthrodesis. In other finger MP joint dislocations, the Kaplan's concept to prevent the reduction was confirmed. But reduction of torn volar plate and incision of transverse metacarpal ligament were sufficient to reduce the dislocation with gentle longitudinal traction during the operation. In two cases of little finger MP joint dislocation, the ruptured radial collateral ligaments were noted after open reduction and it must the repaired to prevent the finger instability later. Their overall end results were good without any significant restriction of MP joints motions and finger instabilities. CONCLUSION: One or two times of closed reduction with proper local anesthesia could be tried, but simple reducible dislocation can be converted to complex irreducible ones by the inappropriate traction method, and so proper reduction technique by closed or even in open way is important with the knowledge of anatomical obstacles to prevent the reduction of the metacarpophalangeal joints.