1. Partial diastasis of the tibio-fibular syndesmosis is believed to be common, but it is often overlooked as a cause of recurrent sprains of the ankle. 2. The treatment of recurrent sprains of the ankle by stabilising the inferior tibio-fibular joint with a lag screw is described. The method has been used in seventy-five patients aged between sixteen and sixty-five years. The longest follow-up has been six years.