Introduction: Syphilis is a sexual and vertical transmitted disease. Its incidence is increasing in Europe, particularly, in Portugal., Material and Methods: A descriptive, retrospective study was performed based on positive treponemal tests from January to December 2013, at the Santa Maria Hospital, Lisbon. In-patients and out-patients evaluated in medical appointments and at the emergency department were included. We proceeded to epidemiological characterization, disease classification and definition of risk factors., Results: We obtained a sample of 580 patients, of whom 51 with no clinical data and 45 with false positive serologies were excluded. There was a predominance of male patients (75%) and a mean age of 47 years. Most (59%) had syphilis successfully treated in the past and 3.7% were in follow-up. We recorded 13 primaries syphilis, 71 cases of secondary syphilis, 40 cases of early latent syphilis, 49 unknown duration syphilis and five cases of late latent syphilis. In the early syphilis group, 42% (n = 124) were HIV-positive and, in 8% both diagnosis were done simultaneously., Discussion: We emphasize the high prevalence of syphilis/HIV co-infection in patients with early syphilis, reinforcing the importance of promoting the use of preventive measures. We obtained 11% of patients with late clinical forms, which are notifiable since June 2014, in Portugal. All serological tests for the diagnosis of syphilis have limitations which emphasizes the importance of clinical-laboratory correlation., Conclusion: Syphilis remains an important public health problem. It is necessary to establish education programs, screening and follow-up strategies to reduce their prevalence and to perform more efficient screening of the partners.