A prospective trial was undertaken on 85 adult patients with open fractures of the distal phalanges of less than 6 hours duration, treated by conventional surgery. They either received no antibiotic therapy, or cephradine in short or long courses. The infection rate was 30% in the group without antibiotics and less than 3% in the treated groups. Three different antibiotics regimes were compared, with no difference in the infection rate: therefore the simplest and surest method, a single pre-operative dose and a single post-operative dose, is recommended.