There are four official European competitions for clubs organized by UEFA:
· Champions League (C1), formerly known as Champions Cup.
· Cup Winners' Cup (C2), merged with UEFA Cup in 1999.
· UEFA Cup (C3), formerly known as Inter-Cities Fairs Cup—until 1971—and former UEFA Cup—until 1999, when it merged with the late Cup Winners' Cup.
The qualification of teams for these tournaments depends basically on their classification in their domestic championships at the end of the precedent season. Until the revolutionary rearrangement of European competitions in 1999, the situation was as follows: as a general rule, the League champion participated in C1, the Cup champion entered C2 (except when this team achieved "the double," League and Cup, in which case it qualified for C1 and the runner-up in the Cup tournament could participate in C2), and a variable number of teams ranked directly below the League winner earned a berth in C3 (in some countries, exceptionally, the League champions were relegated to participate in C3). Intertoto Cup was a "minor" tournament for teams with a worse classification than the former, and the berth assignment depended on a combination of several factors. From season 1999-2000 on, however, this qualifying system underwent some significant changes: the League champions are still entitled to participate in C1, but the top federations in UEFA Country Ranking (see below) are assigned additional berths in Champions League (up to four teams); the participants in C3 are the Cup champions together with the best qualified teams in domestic Leagues.
The berth assignment in C1, C3, and IC for each national federation depends on UEFA Country Ranking (UCR), a classification of countries spanning over 5-year periods, buildt with the average of all the points earned by the participants in C1 and C3 during the same season.
The pairing of teams in the different rounds of European competitions is made by seeding. A certain number of top-seeded teams are bye from the first rounds (or face non-seeded teams) depending on their particular achievements in previous seasons. Only from intermediate rounds on, pairings are directly drafted, without making allowances for seeded or non-seeded teams. Thus, together with UCR (classification of countries in order to determine the number of berths assigned to each one), a ranking of seeded teams is further used to shape the format of C1, C3, and IC.