To study comapatively the physical properties of Korean cotton and American upland cotton, physical properites such as maximum length, effective length, percentage short fiber, percentage dispersion, fineness, tensile strength, and spirality of Korean cotton and American upland cotton have been mesured. The reults of this study are as follows: (1) The maximum length of Korean cotton is within the range of 24.85mm to 30.00mm, the effective length 22.15mm to 27.90mm, the prcentage short fiber 12.06% to 26.72%, the precentage dispersion 13.77%, to 29.05%, the fineness 3.3$mu extrm{g}$/in. to 4.9$mu extrm{g}$/in., the tensile strength 65.303(1,000 psi) to 78.772(1,000 psi), and the spirality 51.2conv./cm to 60.6conv./cm. (2) Classifying the physical properties of Korean cotton by its producing district, the maximum length, the effective length, and the fineness of MogPo 6 are 30.00mm, 27.90mm and 3.3$mu extrm{g}$/in., respectively, the percentage short fiber of Yeocheon 12.06%, the percentage dispersion 13.77%, the tensile strength of Dalsung 78.772(1,000 psi), the spirality of Changyeong 60.6conv./cm, and each of them shows the best values in their field of the physical properties of Korean Cotton. (3) The maximum length of American upland cotton is within the range from 22.35mm to 30.00mm, the effective length 19.55mm to 26.80mm, the percentage short fibre 13.80%, the percentage dispersion 24.83% to 34.03%, the fineness 2.9$mu extrm{g}$/in., the tensile strength 65,649 (1,000 psi) to 85,107 (1,000 psi), and the spirality 47.9conv./cm to 59.7 conv. (4) As shown above, Mogpo 6 of Korean cotton is American upland cotton Good Middling in maximum length, effective length, effective length and fineness, and is approximate to it in spirality.