Eight players, who are generally on the All-Star Game rosters (though this is not necessitated by rule), are selected for the Home Run Derby and compete in a traditional playoff system where the players with the most home runs advance to the next round. Each player gets ten "outs" per round, where an out is defined as any swing that is not a home run in this case. Should a tie exist between players at the end of any round, there will be a five swing swing-off to determine who will advance. Until 2006, the home run count was reset after each round. However, a rule change was made for the 2006 Home Run Derby which causes the home run count for the four players advancing to the second round to carry over. The home run count for the final round is still reset to zero.
Prior to 1991, the Home Run Derby was structured as a two-inning event with each player receiving five outs per inning which allowed for the possibility of ties.
In 2000, a match play format was instituted for the second round. The player with the most home runs in the first round faced the player with the least among the four qualifying players, as did the players with the second and third-most totals. The contestant who won each matchup advanced to the finals. This format was discontinued after the 2003 Derby.
For the most part, the field of players selected consists of four American League players and four National League players. The first Derby in 1985 featured five from each league, and the Derbies in 1986 and 1987 each featured three and two players from each league, respectively. In 1996, the field was again expanded to ten players, five from each league, though in 1997, the American League had six contestants to the NL's four. In 2000, the field reverted to the four-player-per-league format, which it has remained ever since. The only exception has been in 2005, when Major League Baseball chose to change the look of the contest, still having eight players, but with the players representing their home countries rather than their respective leagues. This was commonly looked upon as a lead-in to the World Baseball Classic which was played in March 2006. Bobby Abreu, representing Venezuela, won the first International Derby with a record 41 home runs, including a then-record 24 in the first round, broken only by Josh Hamilton with 28 home runs in 2008. In 2006, the selection of four players from each league to participate in the Derby was resumed.
During the 2005, 2006, and 2007 Home Run Derbies, the Golden Ball was used once a player reaches nine outs. If a batter hit a home run using the golden ball, Century 21 Real Estate and Major League Baseball would donate $21,000 per home run to charity. In both 2005 and 2006, $294,000 was raised for charity, equaling 14 golden ball home runs per year. State Farm continued this in 2007 as they designated $17,000 per home run (one dollar for each of State Farm's agencies), a reduction of $4,000, to the Boys and Girls Clubs of America. In the 2007 event, fifteen golden balls were hit for a donation of $255,000, $39,000 less than the two previous years even though one more home run was hit.
The derby was first nationally televised by ESPN in 1993 on a same-day delayed basis. The first live telecast came in 1998. The event begins at 8 p.m. Eastern time. Although two hours are devoted to the telecast, it is not uncommon for the program to run over schedule. The 2006 and 2007 events, for example, lasted nearly three hours.
Notes: ↑a New single round record. ↑b Voluntarily ended round with four outs
10 Home Runs were hit while the Gold Ball (special balls used when the batters have nine outs) was in play, earning $170,000 for the Boys & Girls Clubs of America.