The analysis of 35 cases of delayed healing of fractures of the upper arm treated from 1981 to 1990 shows that fractures resulting from road accidents (16/35) and comminuted fractures (16/35) are particularly frequent in this group. Delayed fracture healing after conservative treatment (10 patients) was caused mainly by inadequate reduction (4/10) or by the fact that the conservative treatment performed was in fact inappropriate (4/10). Primary osteosynthesis was performed in 25 patients. Inadequate stabilization (9/25) was the most frequent reason for delayed healing, followed by the omission of bone grafting (7/25).