Summary Since 1967, transverse acetabular fractures in 17 patients (13 men and 4 women) have been treated by operative reduction and internal fixation. A follow-up study was made of 8 patients thus treated during 1967 and 1968. The result was found to be poor in one patient, who required arthrodesis; in one patient the prognosis was doubtful. In six cases there had been no early arthrosis, as would have occurred if they had not been treated by operation. Operative reduction and internal fixation are indicated in the treatment of fractures through the weight-bearing part of the acetabulum. Only in very comminuted fractures can this be technically impossible.