Although the requirement to report sexually transmitted diseases was abolished (July 2000), the resurgence of syphilis in late 2001 led to the establishment of a surveillance network involving participating sites (STD clinics, hospital dermatology and venereology clinics, infectious disease clinics, internal medicine clinics, and a Parisian network of private practitioners). Between 2000 and 2002, the number of syphilis cases rose rapidly each year, particularly in the Île-de-France region but also in other regions and across all types of facilities. The Île-de-France region—specifically Paris—is primarily affected by the syphilis epidemic. In fact, more than three-quarters of cases were diagnosed by fewer than half of the participating sites. Three-quarters of people with syphilis were born in France, and half reported at least one previous STI (Sexually Transmitted Infection). Syphilis primarily affects gay men, more than half of whom have been living with HIV for an average of seven years. For the first time, an STI surveillance system in France combines clinical and behavioral data. Nearly half of the patients agreed to answer questions about their sexual practices and preventive behaviors, which were collected using a self-administered questionnaire. This questionnaire provided insight into the patient’s perception of the person responsible for their infection. For half of the gay and bisexual men, this person was unknown. When the source was known, more than three-quarters of them reported having had an anonymous or casual encounter. For one-quarter of them, the encounter had taken place in a sex establishment. Unprotected oral sex was the sexual practice most frequently cited by respondents as having occurred with the likely source of the infection. The resurgence of syphilis necessitated providing information to both the medical community and the general public through STI awareness campaigns. The risk of STIs must be emphasized in HIV prevention campaigns due to their role in facilitating HIV transmission.