OBJECTIVES: To assess adherence in clinical practice of HIV patients switching to emtricitabina+tenofovir disoproxil+rilpivirin METHODS: An observational retrospective cohort analysis, based on administrative databases from four Italian LHUs. The date of the first prescription of emtricitabina+tenofovir disoproxil+rilpivirin between January, 2010 and December, 2013 has been used as the index date. Patients were characterized back in previous 12 months to assess HIV treatments, and followed up after index date for 12 months, date of death, or exiting the database (whatever came first). Non-adherence, as well as selective non-adherence, to antiretroviral medications were calculated using pharmacy refill compliance data in pre/post index date period. Non-adherence measures were expressed in percentages of days spent either without all prescribed antiretrovirals (complete non-adherence) or without at least one of the prescribed regimen components (selective non-adherence) on total days prescribed RESULTS: During the observation period, 87 patients switched to emtricitabina+tenofovir disoproxil+rilpivirin: 10 from Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs), 62 from efavirenz+emtricitabina+tenofovir disoproxil (EFV/TDF/FTC) and 15 from Protease Inhibitors (PIs). Post-switch non-adherence among the 87 patients switching to emtricitabina+tenofovir disoproxil+rilpivirin was around 4%, with small differences according to previous anti-retroviral therapies (4.7% in previously NNRTIs-treated, 4.2% in efavirenz+emtricitabina+tenofovir disoproxil group and 3.2% in patients with previous PIs). For all of them, pre-switch non-adherence showed much higher values: from NNRTIs 20.8% selective non-adherence, 30.5% to all drugs; from EFV/TDF/FTC 10.7%; from PIs 14.2% selective, 25.8% to all CONCLUSIONS: In this preliminary analysis, switching to emtricitabina+tenofovir disoproxil+rilpivirin increased treatment adherence with respect to previous therapies. This phenomenon was highly evident in patients coming from NNRTIs and PIs, who reported an absolute decrease in non-adherence rates of 46.6% and 36.8%, respectively