Fourteen patients with gross anterior instability had the anterior cruciate ligament reconstructed with a bovine xenograft. Major problems with swelling, pain, and synovitis were encountered in 13 patients, of whom 3 developed a synovial fistula. Histologic evidence for allergic reactions was found in 3 patients. Revisional surgery had to be performed in 10 patients because of substantial problems or rupture of the graft. At 3 years, there was only one possibly functioning graft. The 3 nonrevised patients were unstable at clinical examination. This type of reconstruction cannot be recommended for clinical use.