Goals from Leeds United duo Ian Harte and Robbie Keane were enough to give the Republic of Ireland a vital win against Iran.
The 2-0 victory puts Ireland in a strong position with the second leg of the World Cup play off to come in Iran.
A place at next year's World Cup in Korea and Japan is on offer for the winning team, and Ireland now have a good chance of joining England, who have already qualified.
But Ireland had goalkeeper Shay Given to thank as much as Harte and Keane, the Newcastle United star making two superb saves in the second half.
Twice in as many minutes Given denied Karimi a crucial away goal that would have put Iran in a much stronger position.
The second leg is on Thursday in Tehran where more than 100,000 fans are expected to crowd into the stadium to watch the match.