The first phase in using MetaQTL is to create the database to store the QTL mapping experiments. The database here relies on a simple multiple file framework. All the tables of the database are plain text file where the first line contains the labels of the columns and the following lines represents the records. For both the header and the records the fields are separated by a tabulation. The global database (METAdb) consists of 3 tables, the experiment table, the trait ontology table and the marker dictionary table, plus 2 sub databases, the genetic linkage map database (GLMdb) and the QTL database (QTLdb). In the next sections we provide a full description of the tables of the database. We have adopted the following convention to specify each field of the tables: the fields in bold are required, i.e they must be specified in the header of the file while the other can be ignored. For each field we have indicated the type of the value between brackets (e.g string, integer, boolean,...).