| Behçet's syndrome | Recurrent oral aphthae plus two of the following: recurrent genital ulceration, eye lesions, skin lesions, or a positive pathergy test result |
| Chancroid | Painful, friable ulcerations with soft, ragged, undermined edges; surrounding erythema; yellow-gray, purulent exudate; unilateral regional lymphadenitis |
| Herpes simplex virus | Usually groups of painful lesions with or without tender regional lymphadenopathy or constitutional symptoms |
| Lymphogranuloma venereum | Painless shallow ulcerations that heal quickly |
| Syphilis | Painless lesions, typically indurated with a clean base and rolled edges; lesion is usually more than 0.5 cm in diameter; painless regional adenopathy |