Samples of eleven cottons having a wide range of fineness and immaturity properties, as measured by the Arealometer, have been studied for air-flow behavior on an experimental computerized system. Specific surface area and the changes in specific surface area with compression have been obtained across the void fraction of 0.60 to 0.90. Both the specific surface areas, A and A(H), at low high specimen compressions, respectively, have been obtained from the Arealometer. A comparison of the results from the two instruments show very reasonable correlations. These correlations can be enhanced provided changes in fiber orientation and non-homogeneous void fractions generated dorm compression are taken into account.