Urethral gonorrhea is typified by the presence of large numbers of polymorphonuclear leukocytes, which are presumably attracted to the urethra by an as yet uncharacterized chemotaxin. Culture supernatants from three different auxotypes of Neisseria gonorrhoeae, one requiring arginine, hypoxanthine, and uracil (Arg-,Hyx-,Ura-), one requiring proline, arginine (not satisfied by ornithine), and uracil (Pro-,Arg-[Orn*],Ura-), and one requiring proline (Pro-), were tested for their chemotactic activity against leukocytes from men of two racial groups, white and black. These auxotypes were chosen because the Pro- auxotype is isolated more frequently from black patients, and the Arg-,Hyx-,Ura- and the Pro-,Arg-(Orn*),Ura- auxotypes are isolated more frequently from white patients. Chemotaxis was tested in blind-well chambers in the absence of complement; membranes with a pore size of 3 microns were used. The culture supernatants of the Pro- auxotype were the most chemotactic, while those of the Arg-,Hyx-,Ura- were the least chemotactic when analyzed by a three-way analysis of variance: F = 22.83, df = 2.6, P less than .001. There were no differences in migration with respect to the race of the donor. Gonococcal culture supernatants did not require complement for chemotaxis.