Humoral immune responses have been shown for patients infected with H ducreyi. Detection of antibody production to various cell components including whole cell lysate, purified and recombinant outer membrane proteins and LOS have been reported (18-20). For all antigens evaluated, the response is often slow in developing, cross-reactive with other Haemophilus species, and may last a long time after the infection has cleared. The currently reported assays are most useful as epidemiological tools and have limited value as diagnostic tests for chancroid, especially in areas where chancroid is endemic (8). The sensitivity and specificity range of these serological assays is 55% to 100% and 23% to 96%, respectively. Reference laboratories do not have an effective serology test for diagnosis of acute infection with H ducreyi (8).