The effect of an organically modified layered silicate on the rheological, morphological, and structural properties of immiscible polyethylene/polyamide (PE/PA) blends was investigated. The blends have been prepared for PA weight fractions ranging from 10 to 90% and at clay weight fractions from 1 to 6%. Scanning electron microscopy and transmission electron microscopy have been used to study the morphology and the structure of the blends. The dispersed phase size was shown to decrease with increasing clay content up to 2% and tends to stabilize at higher fractions. For PE matrix blends, clay particles were shown to be essentially located at the interface of the two polymers, forming an interphase whose thickness grows with clay fraction. For PA matrix blends with 2% of clay, the interphase thickness is stabilized at 11 nm; further clay addition leads to dispersion of clay within PA. Oscillatory and steady shear measurements have shown that PE matrix ternary blends behaved like polymer blends and underlined the contribution of an interphase at high clay fractions. For sufficiently filled PA matrix blends, a yield behavior was observed. The behavior of PA matrix ternary blends, dominated by the organoclay dispersed in PA, is similar to that of nanocomposites. (C) 2009 The Society of Rheology. [DOI: 10.1122/1.3153551]