Borussia Dortmund survived an early scare to restore their five-point advantage at the top of the Bundesliga with a 6-1 win at Cologne.
Milivoje Novakovic put the hosts in front in the 13th minute, but Lukasz Piszczek replied to level things up for the visitors.
Shinji Kagawa put Dortmund in front just after the break and further goals from Robert Lewandowski and Ilkay Gundogan put the visitors in control.
Kagawa scored again before Ivan Perisic netted the sixth late on as the Westphalians extended their unbeaten run to 21 games, taking them five points clear of Bayern Munich at the top of the table.
Cologne dropped a place as a result of the defeat which sent them below Freiburg on goal difference.
Cologne took the lead in the 13th minute with Novakovic heading past an indecisive Roman Weidenfeller from Martin Lanig's lofted ball.
The goal stung Dortmund into action and they levelled in the 26th minute with Piszczek beating Lanig to Marcel Schmelzer's cross and heading in from six yards.
Jurgen Klopp's side increased the pressure with Sven Bender heading in what he thought was a second in the 41st minute, but the linesman's flag was raised to deny him.
Dortmund needed just seven minutes in the second half to finish off Cologne.
Kagawa blasted a shot into the roof of the net in the 47th minute to take him on to 10 goals for the season before Lewandowski put Dortmund in the driving seat with his 17th strike of the campaign.
Kagawa and Jakub Blaszczykowski were involved in the build-up with the latter squaring for his compatriot to tap the ball in from close range.
Cologne did not give up the fight, but they found it increasingly difficult to break down a Dortmund side who were more than happy to sit on their lead.
Dortmund then set about improving their goal difference.
They scored three more in the space of five minutes with Kagawa and Gundogan breaking with the latter providing the finish to the counter-attack, but he did not put a finish to the scoring at the Mungersdorfer Stadion.
Kagawa made it look easy as he added a fifth with Cologne clearly giving up in the 80th minute and, four minutes later, Perisic beat Rensing in a one-on-one situation to compound Cologne's woes.