A questionnaire-based cross-sectional study was conducted in order to determine how frequently patients attending a genitourinary (GU) medicine clinic use the Internet to diagnose their own symptoms, and to assess the accuracy of their diagnosis. Out of 223 symptomatic patients attending a GU clinic, 101 (45.3%) looked up their symptoms on the Internet. The age difference between those who looked up their symptoms and those who did not was not statistically significant (P = 0.77). Twenty (19.8%) out of 101 patients diagnosed their own symptoms, and 14 (13.9%) patients made the correct diagnosis. Ninety-one (90.1%) patients used the Google((R)) search engine as the starting point for their search. Although the Internet plays an important role in providing health information, the variable quality of health information available limits its use as a diagnostic tool by patients.