A prospective study of 24 patients with displaced intra-articular fractures of the os calcis was performed to compare operative with non-operative treatment. Twelve patients were treated by internal fixation followed by early mobilization, and 12 were managed non-operatively. The patients were assessed 15 months later using eight parameters. Of the 12 patients who were treated by internal fixation, eight had returned to work. Walking distance was significantly longer (4 km) in this group and only one patient needed a change in shoe size. Of the 12 patients who were managed non-operatively, only three had returned to work and eight had a change in shoe size, while the average walking distance without pain was only 1 km. The mean range of subtalar movement was 24 degrees in the operated group but only 12 degrees in the other group (P < 0.05). Radiological follow-up demonstrated partial or full restoration of Böhler's angle in the patients who underwent internal fixation. We recommend plating of displaced intraarticular os calcis fractures through a lateral approach in patients under 40 years of age.