Lionel Messi scored a hat-trick to help see off Espanyol in the Catalan derby and take Barcelona top of La Liga.
Messi collected Ivan Rakitic's pass before curling in the opening goal and added a second from close range following Jordi Alba's pull-back.
The Argentina forward completed his 38th Barcelona hat-trick when he finished off from another Alba cross.
Gerard Pique headed in from a corner before Luis Suarez converted from debutant Ousmane Dembele's low pass.
Dembele, the world's second most expensive footballer who joined from Borussia Dortmund for a fee that could rise £135.5m, came on as a second-half substitute.
Barcelona are the only team with a 100% record and are yet to concede a goal, while La Liga champions Real Madrid are sixth after a 1-1 home draw against Levante earlier on Saturday.