The Grand Slam Cup was a tennis tournament. It was an ITF event (like the Grand Slam events themselves) held every year in Munich, Germany.

The tournament was created in 1990 and was played between late September and mid-October, on an indoor carpet court. Throughout its existence, it became famous for paying the highest prize money in the game, of USD$1.5 million. According to the rules, however, if the tournament was won by a player who had also won one of the Grand Slam events of that same year, the winner would receive a bonus of USD$1 million. So, although the original amount of 1.5 million US dollars was already the biggest prize in the game, as many as 4 players (a quarter of the participants, if each Grand Slam event had had a different winner in the year) had a chance of pocketing USD$2.5 million.

The Grand Slam Cup was not recognized by the ATP, however, and thus participation in it did not count any points for the Rankings and it was not considered an official career title.

After the 1999 edition, on December 9 1999, a compromise was reached between the ITF and the ATP by which the Grand Slam Cup was merged with the ATP World Championship (the year end tournament), which was also held every year in Germany (but in Hannover), giving birth to the Tennis Masters Cup, which would be an itinerary event. Technically this was the end of the competition, since the general view is that the Tennis Masters Cup is a continuation of the World Championship, not the Grand Slam Cup.

The direct result of this compromise can be seen in the qualification rules for the present Tennis Masters Cup, which do not exactly repeat those of the ATP World Championship. The World Championship was meant to include the 8 best ranked players in a calendar year, which theoretically could exclude a Grand Slam champion that might not have been able to keep his rank up for the remainder of the year. Although the present rules also refer to the best 8 of the year, it guarantees access to all Grand Slam champions of the year (they had a guaranteed spot in the Grand Slam Cup). Usually, those champions are also among the best 8, but if one or more are not, they will be included to the detriment of the 8th best player (if it's two champions that need to be included, then the 7th best would also be excluded, and so on – to the limit of the 5th player, since there are only 4 Grand Slam events).

This situation could be observed in the 2004 Tennis Masters Cup (in Houston, USA), where the 8th best player of the year, Andre Agassi, of the United States, was excluded of the event in favor of Gaston Gaudio, of Argentina, who had won that year's Roland Garros but was ranked 10th at the end of the year.

Qualification and form of play

Qualification and seeding for the event had nothing to do with the ATP ranking. The ITF would attribute to players a given numbers of points for their performance in the Grand Slam events (these points were only meant for qualification for the Grand Slam Cup, nothing more). After all four events were over, the ITF would sum up the numbers and the 16 highest results would qualify for the Grand Slam Cup.

The system of play was a simple playoff, except that the first two of the four rounds were best-of-three matches, while the last two (semifinals and final) were best-of-five, and there was no tie break in the final set (third, if best-of-three, fifth if best-of-five).

ITF's Grand Slam Cup points table
Rounds of Grand Slam events only

Champions

Complete Results

1990

1991