Brazil went top of Group E as they opened their Olympic campaign in style with a comfortable victory over tournament newcomers Cameroon at the Millennium Stadium.
Early goals from Francielle and Renato Costa put Brazil in control, before captain Marta with a brace and substitute Cristiane sealed victory.
The South Americans got off to the perfect start as they found themselves 2-0 up inside 10 minutes.
Firstly, midfielder Francielle fired a brilliant free-kick beyond Cameroon keeper Annette Ngo Ndom to give the Beijing silver medallists the lead.
Defender Costa then doubled the advantage as she rose powerfully to head home from Francielle's corner.
Ester came close to adding a third goal for the Samba Queens but her shot from distance was tipped away by Ngo Ndom.
Cameroon had barely registered as an attacking threat during the first half, but their brightest moment saw some excellent trickery from Gabrielle Onguene, only for the striker to push her shot well wide.
Brazil's dominance continued after the break with Marta prodding wide after combining superbly with Thais Guedes.
But the skipper did add a third from the spot after 72 minutes before substitute Cristiane calmly rounded the keeper for the fourth.
Marta then rounded off the scoring by slotting into an empty net from Cristiane's pull back.