The methods employed at present for the diagnosis of chancroid are far from satisfactory. Current textbooks indicate that accurate diagnosis can be based on the clinical features, on the results of skin tests or on examination of stained smears. Most venereologists, however, know that each of these methods is subject to major limitations and errors. Actually at present the diagnosis is usually based on negative dark field examinations for spirochetes and on clinical improvement after institution of sulfonamide therapy. The establishment of reliable criteria for a positive diagnosis of chancroid would unquestionably be of value. The present article is a report on the relative efficiency and usefulness of a number of diagnostic procedures in chancroid. These findings were obtained during an intensive study of a group of 125 patients suspected of having either chancroid or lymphogranuloma venereum. Efforts were made to culture the Ducrey bacillus or to demonstrate the presence