A functional assessment of twelve patients after ankle arthrodesis for post-traumatic arthritis was carried out by means of an extensive clinical evaluation and gait analysis after an average follow-up of eight years. A weighted point system was developed to grade ankle function clinically. The data on gait analysis were examined to determine the effect of arthrodesis of the ankle on the over-all pattern of walking. Under conditions of normal daily living while wearing shoes, all patients functioned well after arthrodesis. The gait-analysis data obtained with the patients wearing shoes showed excellent gait characteristics, and the ankle motion that had been lost was compensated for by: (1) motion of the small joints of the ipsilateral foot; (2) altered motion of the ankle in the contralateral limb; and (3) appropriate footwear. While the patients were walking barefooted, some adverse effects of fusion of the ankle were evident. Velocity of gait was slowed and the length of stride was shortened in all twelve patients. One patient whose ankle had been fused in an equinus position had a back-knee deformity during stance phase, and another walked only on his toes when he was without shoes. The gait patterns of all patients were markedly improved when they were wearing shoes with appropriate heel heights.