Recent measurements have shown that mechanical relaxation peaks commonly observed inn‐paraffins are absent in single crystals ofn‐eicosane (C20H42). This work has now been extended to include polycrystalline samples of several highly pure long‐chain hydrocarbons. Internal friction data obtained for a variety ofn‐paraffins, pure or otherwise, have revealed no low‐temperature &ggr; relaxation. Moreover, the &agr; relaxation peak is suppressed completely by purification. In attempts to induce an &agr; or &ggr; loss peak, several dilute mixtures of othern‐paraffins in pure C20H42have been examined. Only the addition of odd‐numbered shorter chains induced loss peaks. On the other hand, the presence of a branched impurity, in this case the C20H42isomers 2‐methylnonadecane and 10‐methylnonadecane, did induce loss peaks, one of which correlates very well to the &agr; process found in as‐received C20H42. It is proposed here that isomer impurities are an important factor in the mechanics of many of the loss processes in long‐chain hydrocarbons observed both mechanically and dielectrically.