In the present study we show our experience as one of the Centers (center 006) of the Italian Index of Protease Inhibitors (PI). In this multicentric, observational study we studied HIV-positive naive patients for antiretroviral therapy with protease inhibitors. From 8/1/97 to 31/1/98 in our department 64 patients were enrolled and followed up through an electronic medical sheet in order to evaluate efficacy, tolerability, toxicity and compliance of treatment with PI. Our results show a reduction in AIDS-related mortality and a decrease in AIDS defining diseases: in particular data show an increase in CNS pathologies in comparison with other opportunistic events. Moreover, in patients non complaints to therapy, the progression of the disease was more frequent. The side effects more frequently observed during PI treatment were hypertrigliceridaemia and lipodystrophy; gynaecomastia and hyperprolactinaemia were even present, perhaps as expression of direct metabolic action of HAART therapy.