Cork Constitution's grip on the Division One trophy loosened further at Templeville Road as St Mary's College claimed a gritty victory.
Con lost to Young Munster last weekend for their first defeat in 12 AIB League matches and Mary's clinically repeated the trick.
They led 16-0 at half-time – quick hands put Conor McPhillips over for a try and back rower Hugh Hogan also touched down.
Shaun McCarthy booted two penalties and although Con's Richie Lane replied with three successful kicks, the damage had been done.
Scorers:
St Mary's College: Tries: Conor McPhillips, Hugh Hogan; Pens: Shaun McCarthy 2
Cork Constitution: Pens: Richie Lane 3
