<p>Background: The interaction between HIV and <em>Trichomonas vaginalis</em> infection has been widely studied in most developed countries but with scanty information in sub-Saharan Africa. While many of these studies have examined the prevalence of <em>T. vaginalis</em> infection in HIV positive individuals, no study in Nigeria has shown the effect of <em>T. vaginalis</em> on HIV transmission. Therefore, the study aimed to determine the occurrence of HIV in <em>T. vaginalis</em> infected women.<br /> Methods: A descriptive study was conducted among women attending STI clinic at the General Hospital, Badagry, Lagos, Nigeria. A total number of 201 (<em>T. vaginalis</em> infected) women were screened for HIV using rapid diagnostic test kits.<br /> Results: The frequency of HIV in <em>T. vaginalis</em> infected women was 35.8%.<br /> Conclusion: The study showed that <em>T. vaginalis</em> infection in women may be a high risk factor of HIV infection.</p>