Optimal conditions for electrospinning of uniform polyamide 6,6 (PA66) nanofibers were determined by the control of various parameters, such as polymer solution concentration, flow rate, tip-tocollector distance (TCD), applied voltage, and electrical conductivity of the polymer solution. An organic salt, benzyl trimethyl ammonium chloride (C10H16CIN, BTMAC), was added to the solutions for increase of electrical conductivity. When no salt was added to the PA66 solution, the uniform nanofibers were electrospun only at limited conditions, such as flow rate of 0.5 mL/h and electric fields greater than 2.0-3.5 kV/cm. In contrast, by the addition of BTMAC, range of optimal conditions for uniform nanofibers was expanded; uniform nanofibers were obtained at flow rate of 0.5-1.5 mL/h and electric fields greater than 1.3-1.6 kV/cm. This means that the electrospinnability of the nanofibers is improved by increasing electrical conductivity of the solutions. Furthermore, the addition of BTMAC affected the increasing of number average diameters and standard deviation of the nanofibers. On the other hand, the process variables, such as flow rate, TCD, and applied voltage, exerted little influence on the increase of diameters.