Before lateral ankle stabilization, arthroscopic surgery was performed on 54 patients (55 ankles) with chronic ankle instability. All patient charts, x-rays, operative reports, and surgical videotapes were reviewed. A detailed questionnaire was answered by all patients. The study population included 31 males and 23 females, with a mean age of 31 years (range, 14-64 years). The right ankle was involved in 64% of cases. Average follow-up was 9.6 months. Arthroscopic surgery was performed using small joint instrumentation including 30 degrees and 70 degrees 2.7-mm arthroscopes and a 30 degrees 1.9-mm arthroscope. At surgery, 51 ankles (93%) had intra-articular abnormalities including loose bodies (12), synovitis (38), osteochondral lesions of the talus (9), ossicles (14), osteophytes (6), adhesions (8), and chondromalacia (12). The most common arthroscopic procedures were synovectomy, removal of loose bodies and ossicles, excision and drilling of osteochondral lesions, debridement of the lateral gutter, excision of osteophytes, and removal of adhesions and scar tissue. There was a 25% incidence of chondral injuries, which differs considerably from the results of Taga et al., who found chondral injuries in 95% of ankles with lateral instability. Overall, there were excellent or good results in 96% of ankles. The incidence of excellent results was lower in the worker's compensation patients because of a greater incidence of complaints of pain with activity. There was no correlation between the presence of osteochondral lesions or amount of talar tilt and results.