Hampshire will face Somerset while Sussex take on Yorkshire in the Friends Life t20 semi-finals.
The Hampshire-Somerset clash will particularly capture the attention as the two sides renew hostilities for the third finals day in succession.
Somerset won last year's semi-final after a one-over eliminator to partly avenge their defeat in the 2010 final, when the Royals triumphed with the scores level by virtue of losing fewer wickets.
Hampshire came through a tense quarter-final against Nottinghamshire, while Somerset - beaten finalists for the last two years - beat Essex by 27 runs.
Yorkshire, who enjoyed an impressive 29-run win over Worcestershire, will take on a Sharks side whose 39-run win over Gloucestershire was inspired by Scott Styris' astonishing 37-ball century.
Finals day takes place at Glamorgan's SWALEC Stadium on Saturday, August 25, with the order of the semi-finals to be determined in the coming days.