Electrostatic spinning or electrospinning is now a well-known process for fabricating ultrafine fibers with diameters in the submicrometer down to nanometer range from materials of diverse origins. The polarity of the emitting electrode (i.e., the one that is in contact with the polymer solution or melt) can be either positive or negative. In the present contribution, the effects of emitting electrode polarity and some processing parameters (i.e., polyamide-6 (PA-6) concentration, molecular weight of PA-6, electrostatic field strength, solution temperature, solvent type, and addition of an inorganic salt) on morphological appearance and average size of the as-spun PA-6 fibers were investigated. Scanning electron micrographs showed obvious morphological difference between the fibers obtained under positive and negative polarity of the emitting electrode. The main differences were that the cross section of the as-spun PA-6 fibers obtained under the negative electrode polarity was flat, while that of those obtained under the positive one appeared to be round and that the average size of the fibers obtained under the negative electrode polarity was larger than that of those obtained under the positive one. (c) 2005 Wiley Periodicals, Inc.