Harelquins' Jim Evans tackles Tom Shanklin of the visitors
Harlequins (10) 13
Pens: Malone (2)
Cardiff Blues (3) 13
Harlequins and the Blues shared the first draw of this season's Heineken Cup after a closely fought match.
Pens: Blair (2)
The first half was a scrappy affair, lit up only by Nick Easter's burst-through from the line-out to score a try in stoppage time.
The quality of play improved after the break, with Jason Spice's try giving the Blues the lead for the first time.
But Chris Malone promptly kicked Quins level and neither side did enough in the remaining stages to merit the win.
Harlequins dominated the opening quarter but all they had to show for it was Malone's penalty, conceded after Ben Blair had struggled to gather a towering up and under.
Only Spice's expertly timed tackle denied Malone a breakaway try, and he also tried his luck with two drop goals, one of which hit the post while the other was well off-target.
But having weathered the early storm, the Blues worked their way upfield and Blair's penalty levelled the scores.
As the break loomed, neither side had put together a sustained period of flowing play, and the level scoreline was a fair reflection of the game so far.
But Dave Strettle took advantage of Tom James' hesitancy, gathering Andy Gomarsall's bouncing kick to set up an attack near the goal-line.
And from the subsequent line-out, England number eight Easter cruised through a gap in the defensive line to score.
Blair's second penalty kept the visitors in contention and as the game wore on, opportunities began to emerge for both sides.
Strettle followed up Mike Brown's line break but was denied a scoring chance by a wayward pass.
And the Blues instantly turned used the turnover for a thrilling counter-attack, snuffed out only by Chris Robshaw's tackle.
The Blues went ahead for the first time when Ugo Monye's kick failed to find touch and was gathered up by Tom James, who off-loaded to support runner Spice, who touched down.
But almost instantly, Malone's second penalty restored parity.
Just as the game looked certain to end in a draw, the Blues tried to run the ball out of defence and were penalised for a forward pass.
This gave the home fans hope of snatching a late victory, but it was not to be and the points were deservedly shared.
Harlequins director of rugby Dean Richards:
"We had 70% of the line-out possession, our scrum was pretty good and from a territorial point of view it was probably 60-40 - but we didn't capitalise on it.
"At the end we should have just dropped the goal. You couldn't have asked for a better position.
"Gomars [Andy Gomarsall] has said it should have gone. He's held his hands up."
Blues director of rugby Dai Young:
"It wasn't perfect but it's seven points out of 10 and that's a match they could have won. We weren't really in the game for the first 25 minutes.
"There was a lot riding on it and I don't think either side played to their potential.
"We are going to have to be better than we were today."
Harlequins: Brown; Keogh, Strettle, Barry, Monye; Malone, Gomarsall; Jones, Fuga, Ross, Kohn, Evans, Robshaw, Volley, Easter.
Replacements: Brooker, Nebbett, Percival, Hala'ufia, So'oialo, Jarvis, Masson.
Blues: Blair, James, J. Robinson, Shanklin, G. Thomas, Flanagan, Spice, Jenkins, R. Thomas, Filise, Jones, Tito, Molitika, M. Williams, Rush.
Replacements: G. Williams for R. Thomas (64), Sidoli for Tito (64). Not Used: Yapp, Morgan, Sowden-Taylor, Selley, R. Williams.
Referee: Pascal Gauzere (France).