Primeira Liga: Porto 1 Vitoria Guimaraes 0
Yacine Brahimi struck the only goal of the game 14 minutes before half-time to lead Porto to 49 points for the season, six ahead of third-placed Sporting Lisbon, although Lisbon's two leading clubs are yet to play this round.
The result also continued Guimaraes poor run - Rui Vitoria's men led the Portuguese league as recently as the end of November but have only won two of their past 10 matches, and have failed to taste victory in their last four games.
Guimaraes (36) sit fifth after their loss in Porto.
Porto took the lead in the 31st minute when Oliver Torres received a cross from the left but had to turn away from goal.
The Spanish striker fed Brahimi on the left side of the penalty area and the Algerian attacker stabbed his shot under Guimaraes goalkeeper Assis to score.
The visitors struggled to create chances at the Estadio Do Dragao, shooting just once for the match, while Porto, who had 62 per cent possession, managed six shots with two on target.
Sporting will visit Belenenses on Saturday as they try to keep pace with Porto, while Benfica will host Vitoria Setubal on Sunday.