AbstractTropical pyomyositis (TP), a suppurative disease caused predominantly by Staphylococcus aureus, is responsible for 3% to 4% of surgical admissions in some hospitals in certain tropical countries. This study describes the clinical features of 35 patients with TP (20 males, 15 females; mean ± SD age 28.3 ± 14.1 years) admitted to our hospital during a 1‐year period and analyzes the causal association between ancylostomiasis, human immunodeficiency virus (HIV) infection, and TP. Concerning the supposed etiologic association between Ancylostoma duodenale infection and TP, among the 35 patients with TP the stool examination of 22 (62.8%) revealed the presence of eggs of A. duodenale. In a control group of 100 asymptomatic subjects the prevalence of ancylostomiasis was 55%. The Odds ratio between the two groups is 1.38 (exact 95% confidence limits = 0.59 < OR < 3.34). Furthermore, the pus from all TP abscesses (41 in 35 patients) was carefully collected and examined microscopically, but nematode larvae were not detected in any of the specimens. Hence these results do not support an association between ancylostomiasis and TP. With the aim of correlating TP with HIV infection, I carried out a case‐control comparison of HIV seroprevalence among the patients affected by TP and an age‐ and sex‐matched control group of healthy subjects. Eleven patients with TP were HIV antibody‐positive (seroprevalence 31.42%), as were two controls (seroprevalence 5.71%). The matched analysis produced a Mantel‐Haenszel matched Odds ratio of 5.50 and a maximum likelihood estimate of OR (MLE) of 5.50 (exact 95% confidence limits for MLE: 1.20 < OR < 51.07). Among the 11 patients HIV‐seropositive, 9 (81.8%) fulfilled the World Health Organization clinical case definition (CCD) for AIDS, compared with 1 of 24 (4.1%) HIV‐negative subjects. The chi‐square test for difference in fulfilling the CCD for AIDS between patients with TP seropositive and seronegative result was statistically significant (p < 0.0001). It is concluded that TP is a bacterial infection highly significantly associated with HIV infection and thus must be considered a strong sign of stage III–IV of HIV disease.