This paper, part of a larger epidemiological study carried out between 2004 and 2010, analyzed immigrants frequenting the largest Apulian regional hospital (Bari Policlinico). Our aim was to evaluate the perception on the part of undocumented immigrants of their rights of access to the National Health Care services and whether this privilege is actually utilized. An anonymous multi-language questionnaire was distributed to all patients with STP (code number for temporary presence of foreigners) at the immigrant outpatient Infectious Diseases Clinic of Bari from June 2009 to June 2010. Questions were related to nationality, date of arrival in Italy, use of health facilities in the 2 years prior to the compilation of the questionnaire, and their understanding of STP. The patients were also screened for infectious diseases (HIV-Ab, HBsAg, HCV-Ab, VDRL, TPHA and Mantoux). A total of 256/272 patients completed the questionnaire; the meaning of STP was unknown to 156/256 (60.9%) patients, only 54/256 (21%) knew the exact meaning of STP and only 42/54 (76.6%) of the latter knew how long STP was valid. Moreover, 128/256 (50.7%) were aware that doctors from the emergency unit were not allowed to notify police regarding presence of illegal immigrants. Regarding clinical data 3% were HIV+ (8/256), 5% (13 patients) positive for TPHA, 5% for HBsAg, 2% were HCV (five patients). A >10 mm diameter infiltrate of Mantoux test was noted for 44% of patients. A lower prevalence than expected for infections such as HIV, HBV or HCV was noted for immigrants compared to data from their countries of origin. At present, large-scale political solutions to the challenges of facilitating access to health facilities for undocumented immigrants are lacking in Italy. The development of communication systems is fundamental to improving access to health services and to creating links between immigrants and the healthcare system.