Our interest in the role of Haemophilus ducreyi in genital ulceration led us to examine the various media commonly used for the cultivation of the organism. We describe an improved medium for the routine isolation of H ducreyi. In comparative studies using 50 test strains originally isolated in the United Kingdom, Canada, the United States of America, and Kenya, the new medium proved superior to three standard media in requiring a shorter incubation period to first visible growth, giving larger colonies in the same period, and making possible a starch aggregation test which we have found helpful in the presumptive identification of H ducreyi from clinical material.