Nat West holders Gloucestershire were knocked out of the competition as Worcestershire secured a three-wicket victory with seven balls to spare in a tense game at New Road.
Worcestershire were helped in their cause by 21-year-old Ryan Driver, who scored an unbeaten 61 not out to guide his side home at the end.
Gloucestershire got off to a competent start, but were held back by a superb opening spell from Australian Glenn McGrath, who conceded only 23 runs from his 10 overs.
A solid second wicket partnership by Rob Cuniliffe and Jack Russell helped Gloucs to a comfortable position before Cunliffe drove Kabir Ali to long-off after making 69.
Russell was eventually out after scoring 84, holing to deep midwicket off the bowling of Richard Illingworth, as Gloucestershire suffered a batting collapse, finishing on 211-8.
However, Worcestershire got off to a bad start as Paul Pollard and Elliot Wilson fell early on, followed by England one-day squad members Graeme Hick and Vikram Solanki, to leave them at 68-4.
But a spirited partnership of 89 in 20 overs from Driver and David Leatherdale, who scored 53 in 65 balls, helped put Worcestershire back on track.
Driver was helped by a missed chance when he was dropped by Mark Alleyne on 28, but a crucial stand of 16 between Driver and Illingworth helped Worcestershire to end Gloucestershire's monopoly on the one-day competitions.
Scorecard:
Gloucestershire Innings
R J Cunliffe c Illingworth b Kabir 69
K J Barnett c Hick b Kabir 16
R C Russell c Pollard b Illingworth 84
M G N Windows run out 1
M W Alleyne c Rhodes b Lampitt 0
I J Harvey st Rhodes b Leatherdale 5
J N Snape c Ali b Illingworth 6
C G Taylor not out 4
M C J Ball c Hick b Illingworth 10
J M M Averis not out 2
Extras lb3 w7 nb4 14
Total 8 wkts Innings Complete (50 overs) 211
Fall: 1-37 2-146 3-148 4-149 5-177 6-195 7-195 8-208
Did Not Bat: A M Smith.
Bowling: McGrath 10 1 23 0, Kabir 10 0 45 2, Lampitt 10 1 30 1, Leatherdale 5 0 40 1, Illingworth 10 0 43 3, Hick 5 0 27 0.
Worcestershire Innings
P R Pollard c & b Harvey 12
E J Wilson st Russell b Ball 21
G A Hick c Snape b Smith 13
V S Solanki lbw b Smith 7
D A Leatherdale c & b Harvey 53
R C Driver not out 61
S J Rhodes run out 0
S R Lampitt c Russell b Ball 0
R K Illingworth not out 25
Extras b1 lb5 w10 nb4 20
Total 7 wkts (48.5 overs) 212
Fall: 1-14 2-32 3-51 4-68 5-157 6-158 7-158
Did Not Bat: Kabir Ali, G D McGrath.
Bowling: Smith 10 3 39 2, Harvey 9 1 45 2, Averis 8.5 0 41 0, Ball 9 1 31 2, Alleyne 8 0 31 0, Snape 4 0 19 0.
Umpires: J F Steele and P Willey