In late 2000, the French Institute for Public Health Surveillance (InVS) was alerted by a venereal disease clinic (DAV) in Paris to a resurgence of syphilis cases. Investigations conducted by the InVS documented the resurgence of this sexually transmitted infection (STI) in the Île-de-France region and led to the establishment of a voluntary syphilis surveillance system. The objective of this surveillance is to track trends and describe the clinical and behavioral characteristics of patients with this STI. The rapid increase in the number of reported cases between 2000 and 2002, primarily among gay men, led health authorities and organizations to launch prevention campaigns targeting gay men, including, in particular, a large-scale campaign encouraging syphilis screening in Paris in 2002.