Several measurements were performed about 105 cases of normal stress A-P arthrographic findings in adult knee including discoid without tearing or osteoarthritis, those were selected from 166 cases examined arthrographicaliy under same technical condition due to suspicious internal derangement of the knee from October 1976 to March 1980. After stastistical analysis and comparative study about chondrai thickness, chondral index, meniscal size, meniscal index, intermeniscal distance, type of meniscus, communication between knee and proximal tibiofibular joint, following results were obtained. 1. Chondral thickness of normal articular cartilage was not related to joint size, but almost same value individually. Mean chondral thickness In P and P points was 2.90±0.63mm, 2.90±0.62mm, 2.93±0.64mm, 2.92±0.65mm in lateral, medial femoral condyle and lateral, medial tibial condyle in order. Age change was not seen statistically. 2. The size of meniscus was correlated nearly proportional with that of the joint. Mean lateral meniscus size (transverse meniscal length × meniscal thickness) was 12.55±2.50mm × 6.53±0.7mm in male and 10.13±2.25mm × 6.02±0.52mm in female. That of medial meniscus was 9.79+1.54mm × 5.85+ 0.45mm in male, and 7.72±1.64mm × 5.36±0.92mm in female. Age change was not seen statistically either. 3. Mean intermeniscal distance was 60.21x2.74mm in male, 53.34±3.31mm in female and occupied 83% in male, 82% in female of joint size each other. 4. In types of meniscus, normal type was 8.10%, infantile type dlscoid 12.4%, intermediate type 2.9%, primitive type 3.7% each other. 5. Communications between knee joint and proximal tibiofibular joint were seen in 24%.