Analysis of time trends in newly diagnosed HIV-1 infected patients in Slovenia over a 10-year period (1996-2005) showed an increase in the number of newly diagnosed HIV-1 infected patients in 2004 and 2005 as well as increase in the number of newly diagnosed patients with primary/early HIV-1 infection. A retrospective analysis was performed in order to evaluate the clinical, epidemiological, laboratory and virological parameters of primary/early HIV-1 infection presenting with or without acute retroviral syndrome (ARS). Primary/early HIV-1 infection was diagnosed in 33 (19.5%) out of 169 newly diagnosed HIV-1 infected patients during the 10-year period. Most patients experienced ARS, the most commonly reported symptoms being fever, malaise and pharyngitis, followed by rash and lymphadenopathy. Median CD4 cell count was 415 cells/mm3, median CD8 cell count was 865 cells/mm3 and median HIV-1 viral load at the time of diagnosis was 5.1 loglo copies/mL. The increase in the number of newly diagnosed HIV-1 infected patients may be in part due to increased awareness among clinicians of the possibility of ARS, and the possibility of increased awareness of symptoms of ARS among persons at high risk of infection.