Rucksack paralysis is commonly known as compressive injury of brachial plexus between the clavicle and first rib by the shoulder straps of heavy rucksack. In recent years there has been an increase in the use of rucksacks and backpacks by non-military personnel. Author has reviewed 21 patients of rucksack paralysis who visited the Department of Orthopedic Surgery, Po Hang Armed Forced General Hospital from Jul. 1989 to Jun. 1990. The results were as follows:1. There was no significant difference in involved side and patients were tall and slender in comparision to normal person. 2. Sensory changes were main initial symptoms and the major persistent problems were motor impairment. Pain was a rare symptom. 3. The muscles involved in rucksack paralysis were mainly innervated by C5, C6 and the main impairment of joint motion was shoulder abduction. 4. The prognosis for eventual complete recovery of function was good and was inversely related to the initial severity of the impairment and the elapsed time when recovery begun. Most patients obtained complete function of involved upper extremity within ten weeks. 5. The contributing factors of developing rucksack paralysis were the weight of rucksack, the design of rucksack, the duration of wearing rucksack, the terrain which they were patrolling, the way of wearing a rucksack and the adaptation to wearing a rucksack.