Screening and detecting sexually transmitted diseases (STDs) is a form of secondary prevention, which interrupts further transmission as well as progression of the infection and its sequelae. Unfortunately, primary prevention, by means of education and taking safe sex partners, has not been enough to significantly curb the prevalence and high cost of STDs. Bacterial STDs are decreasing in their prevalence whereas the prevalence of viral STDs has increased significantly in recent years. The differential diagnosis for genital ulcers, urethritis, and genital warts is very important. For example, syphilis, chancroid, lymphogranuloma venereum, and herpes simplex for genital ulcer are mistaken for other causes such as Behcet's syndrome, drug eruption, erythema multiforme, amebiasis, trauma, and carcinoma. Confirmatory testings made by cultures, PCR, or serologic studies are important for appropriate treatment and eradication of the disease in both patients and their partners. The physicians treating STDs should make special efforts to be sure that his or her methods of diagnosis and treatment reflect the latest knowledge, since the epidemiologic characteristics and treatment trends are rapidly changing based on newly appearing resistant strains.