The association between AIDS and pyomyositis was recently pointed out in temperate and tropical countries. In Western countries, the patients affected by pyomyositis associated with AIDS in most cases are neutropenic. We compare a group of 17 patients with pyomyositis and AIDS living in temperate climates from the literature, and 11 patients affected by the same association seen by us in northern Uganda. The patients from Western countries were significantly more neutropenic and their mean of the neutrophil count was significantly lower when compared with our group. We suggest that the defective neutrophil function associated with HIV infection play a major role in the pathogenesis of pyomyositis in our patients.