Single-crystalline gold nanorods have been prepared by one-step, seedless solvothermal reduction of HAuCl(4)center dot 4H(2)O in cetyltrimethylammonium bromide (CTAB)/octane + butanol/formamide microemulsions. Formamide provides not only reduction but also sites occupied by Au3+ ion through replacing "water pools" in the traditional microemulsions.