24 teams (the national domestic league champions from the best leagues, and a variable number of other clubs from the most important national domestic leagues). The competition culminated in a Final Four.
Country ranking
For the 1999–2000 EuroLeague, the countries are allocated places according to their place on the FIBA country rankings, which takes into account their performance in European competitions from 1996–97 to 1998–99.[2]
FIBA: In Euroleague, teams finishing 6th in the Second Stage of 1998–99 FIBA EuroLeague (groups E-H) lose a berth for their country in next season. These berths are gained by those countries whose teams reach the Semi-Final Round in the 1998–99 FIBA Saporta Cup. As a general rule, a federation cannot have more than 3 teams in Euroleague. Should a semi-finalist in Saporta Cup provide one more berth for its country, in case it already has 3 berths assigned in Euroleague, this berth will be transferred to the next federation in FIBA Ranking which has 2 teams (as long as one of its teams reached the 1/4 Final Round in Saporta Cup during the same season)..
Team allocation
The labels in the parentheses show how each team qualified for the place of its starting round:
1st, 2nd, 3rd, etc.: League position after Playoffs
(The individual scores and standings of the First stage were accumulated in the Second stage)
If one or more clubs were level on won-lost record, tiebreakers were applied in the following order:
Head-to-head record in matches between the tied clubs
Overall point difference in games between the tied clubs
Overall point difference in all group matches (first tiebreaker if tied clubs were not in the same group)
Points scored in all group matches
Sum of quotients of points scored and points allowed in each group match
Teams in bold advanced to the next round. The numbers to the left of each team indicate the team's seeding, the numbers to the right indicate the result of games including result in bold of the team that won in that game, and the numbers furthest to the right indicate the number of games the team won in that round.