Miscibility was studied for four polyamide blends of 6I/6T [copolymer consisting of 1,6-hexamethylene diamine and isophthalic acid (6I) (70 wt %) and terephthalic acid (6T) (30 wt %)] with MXD6 (polyamide of m-xylenediamine and adipic acid), BAC6 (polyamide of 1,3-bis(aminomethyl)cyclohexane and adipic acid), TR55 (copolymer consisting of nylon 11 (30 wt %), and polyamide of bis(3-methyl, 4-aminocyclohexyl)methane (30 wt %) and isophthalic acid (70 wt %), and CX7323 (polyamide of bis(4-aminocyclohexyl)methane and dodecanedicarboxylic acid), using differential scanning calorimetry, X-ray diffraction method, and electronmicroscopic observation. In quenched MXD6/(6I/6T) and BAC6/(6I/6T) blends, MXD6 and BAC6 components were miscible to 6I/6T, but TR55 and CX7323 components were completely phase-separated from 6I/6T. Interestingly on electronmicroscopic observations, TR55 and CX7323 components were seen as droplets in 6I/6T medium when the content is low, but when 50 wt %, a layered structure was constructed with 6I/6T, reminiscent of morphological structure in block copolymer. (c) 2006 Wiley Periodicals, Inc.