Chancroid, or ulcus molle, is a local, nonindurated, tender ulcer, usually venereal, which is caused by inoculation with Hemophilus ducreyi, a gram-negative bacillus, which appears singly or in short chains and is easily obtainable by smears from the ulcer. It is fairly easy to culture if first innoculated into defibrinated rabbit blood and may then best be grown aerobically on dextrose-cystine blood agar slants.1 INCIDENCE Chancroid is a relatively common venereal lesion and as such presents problems in diagnosis and treatment to the Army Medical Corps. Of its relative incidence during the World War, the Surgeon General Reports show that though it was the least common of the more frequent venereal diseases, comprising 11 per cent of the total, there were 39,044 primary admissions for chancroid in 1917-1918.2 The calculated noneffective rate was 0.65 per thousand. Its greatest frequency was among Indian and colored troops, being 34.68 per