PURPOSE: We wanted to evaluate the clinical and objective results of autologous chondrocyte implantation (ACI) on a femoral chondral defect of the knee. MATERIALS AND METHODS: We evaluated 14 patients who had been operated on with ACI on the chondral defect of the knee between December 2000 and December 2005. There were 11 males and 3 females with the average age of 33 years (range: 17~44 years) and the mean size of the defect was 5.9 cm2 (range: 2.0~10 cm(2)). Seven cases were due to osteochondritis dissecans, and others were due to traumatic defect. The mean follow-up period was 26 months (range: 12~42 months). Lysholm's and Tegner's scores were used for evaluation. A 2nd look arthroscopic examination and a biopsy were carried out in 6 cases and MRI was done in 3 cases for evaluating cartilage regeneration. RESULTS: The mean Lysholm's and Tegner's scores were improved 60 to 84, and 2.4 to 4.1, respectively. According to the ICRS (International cartilage repair society) assessment, the gross appearance of the regenerated cartilage was graded as the following: 1 normal, 1 nearly normal, 3 abnormal and 1 severely abnormal. MRI demonstrated cartilage regeneration in 2 out of 3 cases. There were 2 cases of graft hypertrophy and 1 case of graft adhesion as complications. CONCLUSION: The clinical results were significantly improved according to Lysholm's and Tegner's scores. However, the gross appearances and histological results gave less satisfactory results. We conclude that a more sophisticated surgical technique and the long term follow-up results are necessary.