The purpose of this study is to investigate the physical properties of down and feather assemblage wihch are usually used filled up in a feather quilt. Experiments were carried out on heat transfer under various density, strain which emerges by adding pressure and diffusion of humidity in case of down and feather assemblage respectively, and the results obtained were compared with those of cotton assemblage. The results obtained were as follows. 1) The coefficient of heat transfer and diffusion coefficient of humidity of feather showed the smallest value among tested three kinds of materials, therefore, it is clear that feather assemblage is most suitable for stuffing material in a quilt. 2) Compressibility of feather and down is bigger than that of cotton assemblage. From this result, down and feather are both to be wadded in coverlet, not in mattress.