Studies have been carried out in order to obtain the informations of transverse seam strength, extension in the course direction of plain-weft knitted fabrics and these relationships. The transverse seam strength of plain-weft knitted fabrics increases with values of the gauge of knitter and cover factor of its knitted fabrics, and the most desirable results through this study obtained that the optimum stitch rates on the plain weft knitted fabrics are 7.50 and 8.25 stitches per inch, and vice verse in seam extension. These results were compared with theoretical value and this leads to a conclusion that actual values can be predicted by the theory.