There is a high incidence of syphilis among men in Rwanda. Syphilis is a sexually transmitted disease caused by a bacterial infection. A hallmark of the disease is the development of a sore or ulcer on the genitals. Although diagnosis is generally confirmed by a specialized blood test, laboratory facilities in the African country are limited and diagnosis is often based on the presence of the ulcer alone. Syphilis is not the only cause of genital ulcers, however. To determine the reliability of this inspection method, the sources of genital ulcers were examined in 110 male and 100 female patients. In men, 21 percent of the ulcers were caused by syphilis; 24 percent were chancroid, caused by another bacteria, hemophilus; 17 percent were caused by genital herpes, a viral infection; 11 percent were caused by lymphogranuloma venereum (chlamydia); and eight percent were mixed infections. The remaining were of unknown causes. In women 40 percent of the ulcers were caused by syphilis, while 20 percent were herpes, 19 percent were lymphogranuloma venereum with ulceration and 12 percent were chancroid. Human immunodeficiency virus (HIV) infection was detected in 43 percent of the women and 77 percent of the men. These results represent a minimal estimate of prevalence because many paired samples were lost during shipping. In addition, the silver-impregnation staining method for determining syphilis infections was not a good laboratory method for diagnosis.