The Republic of Ireland are trailing Cameroon 1-0 0 at half-time in their World Cup Group E tie at Niigata's Big Swan Stadium.
Former African footballer of the year Patrick Mboma lashed home his 24th international goal six minutes before the interval to bring a cagey match to life.
The goal came after Cameroon's sprightly striker Samuel Eto'o, who had been torturing the Irish defence, burst down the right flank and turned past Steve Staunton and squared to Mboma on the edge of the six-yard area.
The Sunderland player's finish was ruthless, coolly placed beyond scrambling keeper Shay Given to put the reigning African and Olympic champions into the lead.
Ireland almost equalised on the stroke of halftime when an Ian Harte freekick was deflected by Cameroon captain Rigobert Song forcing Boukar Alioum into a smart save.