Polyaniline (PANI) dispersions with different assembly structure were prepared using sodium dodecyl benzene sulfonate (SDBS) as surfactant. Based on the images from the microscopy, it was found that the assembly structure of the PANI dispersions could be changed with different preparation conditions, including the concentration ratio of SDBS to HCl, SDBS to aniline and aniline to ammonium persulfate. UV-Vis spectra, conductivity and size distribution of the dispersions were also measured. The dispersions showed good stability and existed without precipitate at least half a year. (c) 2006 Springer Science + Business Media, Inc.