Since December 1986 all patients with recent ligamental or osteochondral detachment and all with chronic insufficiency of the fibular ligament have undergone functional treatment in the form of taping for 6 weeks after primary operative (n = 60) or conservative (n = 40) management. A total of 100 patients (54 m/46 f, 7-60 years) were included in a prospective study. After immobilization of the ankle in a plaster cast for between 7 and 10 days the first, modified, tape was applied, which was normally changed after a period of 14 days. Interruption of functional treatment because of complications due to with the tape was not necessary. Return to work was possible after an average of 22.8 days. Clinical examination after 5-23 months showed excellent results in 84.3%, good results in 12.9% and unsatisfactory results in 2.7%, but no chronic instability was seen in any of the 100 patients. Standardized stress X-rays (15 kp) yielded values for talar tilt and for anterior drawer that were comparable with those in the uninjured ankle. In conclusions, in comparison with other orthoses, the stability of tape applied by a modified technique is secure enough to allow healing of ruptured ligaments in the ankle. Very little patient compliance is needed. Taping is the most economical form of functional treatment. No physiotherapy is necessary. The period of inability to work can be reduced significantly. Functional treatment by taping can be started as little as 7-10 days after injury or operation.(ABSTRACT TRUNCATED AT 250 WORDS)