The Saints demonstrated intent and purpose as they dumped Queen of the South and kept their challenge to the other first division front runners right on course.
Queens put a lot of effort into the match in a bid to lift themselves away from the bottom of the table, and they started the show with John O' Neill blasting a shot against a defender and then heading over a cross from Paul Burns.
But it was St Mirren who broke the deadlock after 21 minutes when Queens failed to clear a corner from the left. The ball bounced in front of the six-yard line, and Simon Lappin hit it on the turn, giving the Dumfries keeper no chance.
Queens were unlucky not to snatch an equaliser just before the interval when Derek Lyle beat the defence to a cross from William Gibson, but his header hit the bottom of the post with the keeper well beaten.
St Mirren missed a great chance to go further ahead just after the break when the Dumfries keeper pulled off a tremendous save from Hugh Murray, and the ball rebounded to Stewart Kean who smashed it wildy over the bar.
Queens lost Lyle within 10 minutes of the restart, as he was stretchered off with his left leg in splints after going down following a tackle in the box. But despite this, they showed a lot of spirit and a strong fight to get back into the game.
But Saints were always dangerous on the break, and Murray came close with a shot which went just outside the post.