Cork City made it ten matches unbeaten when they recorded an important win over second in the table Shamrock Rovers in front of over 4,000 fans at Turner's Cross.
The only goal was scored by the in-form Denis Behan who headed home a Liam Kearney cross after 34 minutes to notch his eighth goal in five games.
The win moves Cork level with Rovers, who they trail on goal difference, but they have a game in hand and now have a great chance of winning a UEFA Cup spot.
Rovers had to select their team without suspended goalkeeper Barry Murphy and Paul Shiels, who were both sent-off in the 3-0 defeat against Bray Wanderers on Tuesday night.
The club's goalkeeping coach Stephen O'Brien took over between the posts with Danny O'Connor returning from suspension also included in the Rovers starting eleven.
Cork, who made it nine games unbeaten with a fine win against Derry in the Brandywell last Friday, also made changes with Colin Healy back from suspension and Gareth Farrelly returning from a hamstring injury. The players to lose out were Colin O'Brien and Leon McSweeney, who were on the substitutes' bench.
Rovers, playing a flexible 4-5-1 formation, started the sharper side as they created a couple of early chances; the best saw a John Martin cross finding Ger Rowe, whose shot brought a diving save from Michael Devine.
But then Behan struck again when Cork created a very good lead goal. Joe Gamble and John O'Flynn combined on the edge of the area, Gamble then played in Liam Kearney who sent a perfect cross to the far post for Behan to head beyond O'Brien.
There were very few chances between two well-matched sides after the break, until Tadgh Purcell almost equalised for the visitors.
The Hoops' top scorer sent a shot across goal which beat the diving Devine and rolled inches wide.
The victory was Cork's first over Rovers this season, and with a visit to UCD on Monday night, they could move into second place on their own behind leaders Drogheda.
Cork City: Devine; Horgan, O'Callaghan, Murray, Woods; Farrally,
Gamble, Healy, Kearney; Behan, O'Flynn.
Substitutes: McSweeney for O'Flynn 75 mins, Softic for Farrelly 88.
Shamrock Rovers: S O'Brien; G O'Brien, Clarke, Reynolds, Ferguson, O'Connor, Martin, McGill, Purcell, Rowe, Cassidy.
Substitutes: Mulhall for Martin 57, Doyle for Reynolds 73, Langtry for Cassidy 88.
Referee: Hugo Whoriskey.
