The HIV epidemic has brought renewed interest to sexually transmitted diseases. This attention has focused in particular on the diseases characterized by genital ulcers that are common in the developing world — chancroid and syphilis — because of the evidence that they both facilitate HIV transmission. Both diseases have been characterized in the past decade by resurgences in the industrialized world, particularly in the USA. The frequent association of chancroid and syphilis with HIV infection has created diagnostic dilemmas for syphilis and therapeutic dilemmas for both. Research into the prevention and control of both diseases is urgently needed in both the industrialized and developing worlds.