When a water-soluble polymer and surfactant with addition of salt are mixed in water solution, the specific structures (aggregates) are formed, in which polymer film is formed around micelle. In a pipe flow, such aggregates take preferred orientation, according to minimum resistance principle. When the Reynolds number increases, the aggregates elongate. In this work, poly(ethylene oxide) (PEO)-cetyl trimethyl ammonium bromide (CTAB) complex formation and its effect on drag reduction was studied. It was found that PEO-CTAB aggregates reduced drag much more efficiently than these substances alone. Structure degradation appeared later and the drag reduction existed longer. Moreover, damaged structure could be partly rebuilt. (c) 2007 Elsevier B.V. All rights reserved.