After Cardiff's victory over Newport by 20-14 on Friday evening, the other three quarter-finals on Saturday saw victories for Llanelli and Pontypridd in the afternoon and Ebbw Vale in the night match.
Wales scrum half Robert Howley had scored the try that took Cardiff to a 20-14 win over holders Newport at the Arms Park and it was Cup kings Llanelli who overcame Bridgend to win by 46-24.
Bridgend struck early with tries by Adrian Durston and Aisea Havili, but Llanelli stormed away in the second half as Ian Boobyer touched down two of their five tries and outside half Stephen Jones kicked 21 points, while former Scarlet, Craig Warlow, notched 14 for Bridgend.
Pontypridd full back Brett Davey kicked five first-half penalties that in the end proved the difference against a game Caerphilly side. Pontypridd won
46-31 with centre Sonny Parker and the Caerphilly forward Andrew Williams both grabbing braces of tries.
A magnificent effort by Pontypool saw them almost add Ebbw Vale to their scalps after having already knocked out Swansea. The Vale won 27-22 thanks to a late try by centre Paul Matthews. Kickers Gareth Cull and Byron Hayward had fought a good duel and Pontypool Park was aflow with a splendid crowd for the evening match.
The draw brought out Pontypridd first and then their opponents, Cardiff, while Llanelli were drawn against Ebbw Vale or Pontypool, but a few hours after the draw it was Ebbw Vale who won through.
DRAW for PRINCIPALITY CUP SEMI-FINALS:
(both to be played at the Millennium Stadium, Cardiff)
LLANELLI vs EBBW VALE 3pm
PONTYPRIDD vs CARDIFF 5.30pm
Pontypridd and Cardiff have met three times in the Cup - Pontypridd won 9-7 home in 1978/79 and 13-6 away in 1979/80, while Cardiff won 8-6 in the 1993/94 semi-final.
Llanelli have beaten Ebbw Vale in all their five previous meetings - 10-4 in the 1975/76 semi-final; 15-9 home in 1979/80; 41-0 home in 1987/88; 19-12 in the 1997/98 final at Bristol and by 38-26 in a 1999/2000 semi-final.