Substitution of the central third of the patellar tendon for the deficient anterior cruciate ligament was performed in 12 dogs (24 knees). In one-half of the knees the patellar tendon grafts were "augmented" with a 4-mm woven Dacron graft. It was hypothesized that Dacron augmentation would protect the patellar tendon graft during its revascularization stages. This was not the case, however. Only once did a Dacron ligament graft demonstrate superiority over the nonaugmented graft; indeed, five of the augmented grafts performed significantly worse.