In this paper a survey about the information tool called "Italian OPACs. List of catalogues (OPAC) of Italian libraries available on the Internet" (accessible from AIB-WEB site at http://www.aib.it/aib/lis/opac1.htm) is described. This paper was presented at AIB/CNSBNT conference "SBN: Which organization for which services?", Florence, Via della Torretta 16 (University of Florence), 16-17 April 1999. This paper is divided in 5 parts: 1. Analysis of the Italian OPACs situation 2. Types of access to OPACs 3. Union catalogues: real ones and virtual ones 4. Independent SBN Polo interfaces in Italy 5. SBN Union catalogue from a closed system to an open system: demonstration of a "simulation"