Heterophil chemotaxis, in response to chemotactic factors generated by three different strains of staphylococcal bacteria, was measured using the modified Boyden-chamber technique. Heterophils were obtained from healthy 6-to-8-week-old broiler chickens. Each bacterial strain generated factors that were chemotactic for chicken heterophils. Factors generated by two pathogenic isolates of Staphylococcus aureus, however, induced significantly greater chemotaxis in chicken heterophils than those generated by a nonpathogenic Staphylococcus isolate.