Infrared spectroscopic analytical determinations of various acrylic, nylon and A/N blended fibers were investigated by potassium bromide pressed disc technique. Quantitative comparison was carried out on the commercial A/N blended samples with the IR technique and solvent method (KS K). The functional groups in blended fibers is easily detected by the use of characteristic absorption band. These spectra can be used to measure the content of blended fibers by using the ratio of NH stretching band (3070 cm-1) of Nylon and CN stretching band (2240 cm-1) of acrylic fibers. (Received Sept. 22, 1971)