One hundred and ninety consecutive patients (222 fractures) who had an extra-articular fracture of a long bone as a result of a low-velocity gunshot were randomized into two groups on the basis of the method of administration of antibiotics. Group 1 consisted of 101 patients (120 fractures) who were managed with intravenous administration of cephapirin sodium and gentamicin for three days. Group 2 comprised eighty-nine patients (102 fractures) who were managed with oral administration of ciprofloxacin for three days. The two groups were comparable in terms of the age of the patient, the locations of the fractures, and the time from the injury to the commencement of antibiotic therapy. Injuries that needed operative débridement or fixation were excluded. All patients were followed until the fracture had healed.Two infections developed in two of the ninety-nine patients (118 fractures) who completed the study in Group 1, and two infections developed in two of the eighty-seven patients (100 fractures) who completed the study in Group 2. With the numbers available, there was no significant difference in the rates of infection (2 per cent for both) between the two groups. All four fractures that were complicated by infection were located in the distal half of the tibia.We concluded that oral and intravenous administration of antibiotics were equally effective for prophylaxis against infection after an extra-articular fracture from a low-velocity gunshot.