Undisplaced radial head and neck fractures are consistently described with no long-term deficits. The aim of this study was to evaluate specifically the long-term outcome of displaced Mason type I fractures, which have not previously described. Twenty women and twelve men, with a mean age of 46 years (range, 22-69 years) when they sustained a displaced Mason type I fracture, were reexamined at a mean of 21 years (range, 15-33 years) after injury. All were treated nonoperatively. Twenty-nine individuals had no subjective complaints, whereas three had occasional elbow pain. There was no objective impairment, and none had elbow osteoarthritis, defined as reduced joint space, whereas there was more radiographic degeneration in the formerly fractured elbow than in the uninjured elbow (85% vs 4%, P < .001). We conclude that the long-term results of nonoperatively treated displaced Mason type I fractures of the radial head and neck are predominantly favorable.