Both teams boast an impressive record in continental competition, with Northampton having won the Heineken Cup back in 2000 and the Amlin Challenge Cup in 2009 and Quins having triumphed in the second tier on no fewer than three occasions.
No side has been more successful than Harlequins when it comes to the Amlin Challenge Cup thanks to title-winning seasons in 2001, 2004 and 2011 and they will head to the East Midlands full of confidence despite the fact that the Saints have home advantage.
Quins made light work of playing away from home in the last round of this year's competition as they saw off French giants Stade Francais 29-6 at the Stade Jean Bouin. Conor O'Shea's troops were simply superb in Paris but that special success isn't the only big away win they have pulled out of the bag in Europe in recent times. They won twice on the road in this season's Heineken Cup - at Racing Metro and the Scarlets - and did the unthinkable at this stage of their 2011 Amlin Challenge Cup winning campaign when they triumphed against Munster at Thomond Park.
The Londoners have been in impressive form of late as well, with their win over Stade followed by back-to-back victories against fellow Premiership play-off contenders Sale Sharks and Leicester Tigers. It is Northampton who have had the upper hand when the two teams have met in the league this season, though, with the Saints winning 23-9 at Franklin's Gardens in January and 13-6 at the Twickenham Stoop in September.
Northampton ended a three-match domestic losing streak with a bonus-point win at home to London Irish at the weekend and, like Quins, they had to win on the road to make it through to this stage of the Amlin Challenge Cup having qualified for the quarter-finals via a runners up spot from Heineken Cup Pool 1. They cruised to victory at Sale Sharks in the last eight and haven't lost a match in the Amlin Challenge Cup since they were beaten by Worcester Warriors in the 2006 quarter-finals.
The last time they hosted a European semi-final, Saints edged past Saracens 16-13 in a nail-biting tie that kept them on track for glory five years ago.
- Harlequins are the only club in the Heineken Cup or Amlin Challenge Cup this season to not have had a player shown either a yellow or red card.
- Saints have won 12 of 15 home games in the Amlin Challenge Cup with defeats against Worcester Warriors (2006 QF), Connacht (1997 pool) and Narbonne (1997 QF) the only blemishes to this record.
- Harlequins and England captain Chris Robshaw is the only player from his club to have played every minute of this season's European campaign.
- The two clubs have never met in European competition before.
- This is the first time in the history of the Challenge Cup that all four semi-finalists are previous tournament champions - Northampton Saints 2009; Harlequins 2001, 2004 and 2011; London Wasps 2003; Bath Rugby 2008.
- Over the past four seasons, clubs with home advantage have a 50% success record in Amlin Challenge Cup semi-finals.
- The last time four English clubs reached the tournament semi-finals was in 2008 when Bath Rugby defeated Sale Sharks 36-14 and Worcester Warriors got the better of Newcastle Falcons 31-16.
- The biggest tournament semi-final win was recorded by Sale Sharks when they defeated Connacht Rugby 59-9 in 2005.
- On the three occasions that Harlequins have reached the semi-finals - 2001, 2004 and 2011 - they have gone on to lift the trophy.