Fauna Italia, the checklist of the species of the Italian fauna, lists all species known up to the year of its publication (Minelli et al., 1993-1995). The work is divided into 110 issues; in every issue, taxa are ordered following the systematic sequence at least above the genus level; within genera, species are usually listed following the alphabetical order. Every species in the checklist is identified by a numerical code including three parts (code of the issue, code of the genus, code of the species); every part is formed by three digits. The codes of genera and species have an extension which allows new species to be inserted without changing the order of the whole list.

The checklist has a very simple structure including some important information. The choice to keep the information complexity to a minimum allowed the completion of the project; similar projects started in other European countries, very rich in data and information, remained incomplete.

The information included in the checklist consisted of (1) distribution of terrestrial and freshwater species in 4 geographical regions of the Italian territory (North, South, Sicily, Sardinia), (2) distribution of marine species in 3 areas (western basins, upper and middle Adriatic sea, remaining basins), (3) status of endemic or threatened species, and (4) concise data on the host species (for parasites) and nesting (for birds). Notes and synonymy are reduced to a minimum.

The checklist was recently transformed into a hierarchical database (Stoch, 2000); the species were ordered in a simple tree structure similar to Windows® Explorer. The aims of the program are as follows: a) the data set is organized following a hierarchical structure which reproduces the classification of animal taxa following the checklist; b) the tree is user-friendly, and may be used also by the non-taxonomist. The hierarchical structure of the database was achieved giving a code to the taxonomic categories above the genus level (phylum, class, order, family); moreover, subspecies were coded as well. The database is relational and includes only two linked tables: the first tables includes taxa above the genus level; the second one includes genera, species, and subspecies, and other information on species distribution and notes. Fauna Italia provides taxonomic information to the World Register of Marine Species (WoRMS).