Unstable Colles’ fractures have an inherent capacity for loss of reduction or shortening, or both. The istability can be recognized by the presence of much comminution, severe dorsal angulation(20 degrees or more), or extensive intra-articular involvement. It is difficult to align the fracture fragments and to maintain the reduction. In twenty-nine patients with unstable Colles’ fracture from Jan. 1982 to Mar. 1984, several invasive methods were used. The results were as follows: 1. Among 147 patients with Colles’ fractures 29 patients(19.7%) had unstable fractures. 2. Colles’ fracture was occurred more frequently in women(77%) and in 6th and 7th decades(56%). Unstable fractures showed no significant age and sex related propencity. 3. Mechanism of injury caused unstable Colles’ fractures were fall on the outstretched hand(25 patients), traffic accident(3 patients) and crushing injury(1 patient). Open fractures were shown in 4 patients among the unstable fractures. 4. Most of the unstable fractures were comprised of type VII and VIII(49%) but type I and II fractures with marked comminution or displacement also showed instability. 5. Complications were such as, redisplacement of the fractures, temporary neuropathy of the median nerve, compartment syndrome, Sudeck’s atrophy, and shoulder-hand syndrome. 6. Overall assessments showed excellent in 4 patients, good in 16 patients, fair in 7 patients and poor in 2 patients. 7. Overall results were mainly correlated with initial severity of the injury and anatomical restoration of the fractures.