Northampton totally dominated Harlequins in a one-sided contest, with the Saints' back row of new skipper Corn Krige, Andrew Blowers and Grant Seely rampant.
The Quins had flattered to deceive with a fifth-minute try, but Northampton were obviously the better side.Fly-half Andy Dunne burst through to send Will Greenwood over - despite the attention of two defenders - giving the home side an early lead.
The Saints hit back with four first-half tries - three converted by Paul Grayson, who had opened their reply with an 11th-minute penalty - to secure their bonus points before the interval.Number eight Seely showed the footwork of a half-back to exploit some shoddy defending and touched down between the posts.
Then Greenwood and Dunne were left standing as centre Marc Stcherbina went through before off-loading to Blowers, who sent Johnny Howard over.
A superb reverse pass from Howard to Blowers, who despatched England left-wing Ben Cohen on a straight run for the posts, provided the third before Grayson and full-back Bruce Reihana combined to send John Rudd over in the right corner.
It could have been worse - Northampton had two tries disallowed. The scoring spree was interrupted only by Dunne's penalty midway through the first half for Quins, but Northampton increased their lead to 34-8 in the 46th minute when Mark Tucker made the most of a three-man overlap to touch down.
Even Northampton's replacements got in on the act. Shane Drahm, on for Grayson, kicked two penalties and Darren Fox, who took over from Blowers at half-time, forced his way over for a 73rd-minute try.
Rudd was shown the yellow card for a high tackle on Ugo Monye, the Harlequins left wing, who took his revenge with a 79th-minute try. But that was little consolation for the outplayed Quins.
HARLEQUINS: Duffy; Monye, Greenwood (Staunton 27), Deane (Diprose 54), Keogh (Harder ht); Dunne, So'oialo; Worsley (Jones ht), Hayter (Tiatia ht), Dawson, Rudzki, Miall (Winters 58), Molitika, Sheriff, Vos.
NORTHAMPTON: Reihana; Rudd, Tucker (Human 75), Stcherbina, Cohen; Grayson (Drahm 58), Robinson (Howard 18); Smith, Thompson (Richmond 75), Kempson, Boome (Lord 75), Browne, Blowers (Fox ht), Krige, Seely.
Referee: T Spreadbury (Bristol).
