Over a 6-year period (1977-1983), 59 patients with 61 tibial shaft fractures were treated by external fixation. Of these patients, 42 with 42 fractures were followed up until solid union. Thirty-seven fractures were caused by high-energy impact, mainly road accidents. Seventeen fractures were closed and 25 were open. In 33 patients an external quadrilateral frame system was applied primarily, and in the remaining nine within 1-2 weeks. No predrilling was done, and in 16 patients nonthreaded connection rods were used throughout the period in the fixator. The process of union was monitored by repeated noninvasive measurements of stability. Average time form injury to dismantling of the external fixation was 5.2 months (range 2-12.5 months) and time-to-union for the whole series was 10.0 +/- 5.5 months (range 4-31 months). Sixteen fractures failed to unite. Compared with other published series treated by external fixation, the incidence of non-union in the present series is high. On the basis of the present findings it is concluded that a compression device should be mounted either primarily or as soon as possible during the process of union, and that compression should be applied at regular intervals. If an external fixator is used, the surgeon must bear in mind the possible complications. It is probably safer to reduce rather than to prolong time-to-removal of the external system.