The meniscus performs critical functions within the knee, and its loss frequently leads to osteoarthritis and irreversible joint damage. Because prosthetic replacement of the meniscus has proven ineffective, the authors used tissue engineering techniques to develop a resorbable collagen scaffold (collagen meniscus implant) that supports ingrowth of new tissue and eventual regeneration of the lost meniscus. Eight patients underwent arthroscopic placement the collagen meniscus implant to reconstruct and restore the irreparably damaged medial meniscus of one knee. Seven patients had one or more prior meniscectomies, and one patient had an acute meniscus injury. Patients were observed with frequent clinical, serologic, radiographic, and magnetic resonance imaging examinations for at least 24 months (range, 24-32 months). All patients underwent relook arthroscopy and biopsy of the implant regenerated tissue at either 6 or 12 months after implantation. All patients improved clinically from preoperatively to 1 and 2 years postoperatively based on pain, Lysholm scores, Tegner activity scale, and self assessment. Relook arthroscopy revealed tissue regeneration in all patients with apparent preservation of the joint surfaces based on visual observations. Histologic analysis confirmed new fibrocartilage matrix formation. Radiographs confirmed no progression of degenerative joint disease. The collagen meniscus implant is implantable, biocompatible, resorbable, and supports new tissue regeneration as it is resorbed. This tissue seems to function similar to meniscus tissue by protecting the chondral surfaces.