The solitary bone cyst is most frequently located in the upper arm and the average age of the affected patients is between 7 and 9 years, thus perceptibly lower than in cases where solitary bone cyst occurs elsewhere, where the average age is 15. The tendency towards recurrence before 10 years of age is twice as great as the tendency after that age. Investigation of the results obtained from the treatment of 26 patients suffering from solitary bone cyst of the humerus showed a recurrence rate of 55% after curettage and filling-in of the defect with cancellous bone grafts, whereas after total subperiosteal resection and bridging the defect with an autologous tibia graft the corresponding recurrence frequency was 7%. The average duration of the plaster cast fixing period after resection treatment was 18 days longer than after curettage, but the low rate of recurrence in the first-mentioned case makes up for this disadvantage. It is absolutely essential to retain the periosteum in cases of cyst resections. The defect is bridged over by an autologous tibia graft, but fibula grafts are also suitable for bridging the defect. Osteosyntheses are not necessary with latent cysts. In the case of active cysts screws, wire loops, Kirschner wires, and thin Küntscher nails can be used as temporary stabilisation means. Plate osteosyntheses constitute an exception. Complete removal of the cyst by resection is the most certain prophylactic method against recurrence, and hence the most reliable form of treatment of the solitary bone cyst of the humerus.