1. The results of internal fixation are described in 470 tibial shaft fractures.

2. The immediate internal fixation of compound fractures was followed by so high an incidence of serious complications that the use of this method is not recommended. The immediate internal fixation of fresh closed fractures was also followed by many complications.

3. Delayed rigid internal fixation proved satisfactory for difficult fractures in which an acceptable reduction could not be obtained by closed means ; skeletal traction was of value in such fractures until the skin was soundly healed.

4. Delayed internal fixation reduced both the healing time and the complications.

1. The results in 211 fractures of the shaft of the femur in adults treated by internal fixation have been reviewed.

2. A comparison has been made between the effects of early internal fixation within the first six days of injury and delayed fixation.

3. Eighty-five fractures treated by early fixation gave a rate of non-union of 23 per cent; in 126 fractures treated by delayed fixation the rate was 0·8 per cent.

4. Delayed operation is therefore advocated for the majority of femoral shaft fractures for which internal fixation is indicated.

The place of internal fixation in the treatment of fractures of the shafts of the radius and ulna in adults is discussed, and the results in 130 fractures treated by internal fixation are reviewed.

Non-union was found to be the most frequent and serious complication after internal fixation.

The incidence of non-union can be greatly reduced if operation is delayed for at least one week, and preferably two to three weeks after injury.

Evidence is presented to support the value of delayed operation in the promotion of union of fractures.