The object of my research is to inquiry into the immediate constituent and techniques of underwear after looking into basic theory of underwear, techniques by materials classified according to the matter of elasticity, and studying flat pattern and draping which are basis of corset and brassiere structure focusing on corsetry among underwears and production techniques. Various papers are referenced for theoretical study and the elements and techniques of underwear are analyzed based on photographical materials. This paper concludes as follows. To make the flat pattern of corset and brassiere fit to the body tightly, design dart two times without any space and draw smaller than the body. To support the breast sufficiently, move the side seam 1¼″ to the front panel and the seam should pass the apex in all occasions. For draping, dart should be added into short of elasticity materials in the past but dart is no use these days since the material today is extremely elastic. It is possible now to show the body line with only the seam or a pattern. In a case of elastic material, set the elastic direction to the grain line and have a draping as pulling from the center to the out side. As production technic, for an hem, put a zigzag stitch in elastic materials with a 10-20% short elastic band, pulling the band. Then make 3/16″-1/4″ short inseam.