Nicky Forster's ninth goal of the season steered Reading into the last 16 of the Carling Cup as the Royals edged out brave Huddersfield at the Madejski Stadium.
Forster headed home Andy Hughes' cross 10 minutes from time to earn the Royals a deserved but hard-fought win over Peter Jackson's battling Terriers.
Huddersfield, having already taken two First Division scalps in Derby and Sunderland, looked confident from the off. But in a first half of precious few chances it was Reading who came closest to breaking the stalemate.
Former England winger John Salako volleyed wide from a Scott Murray cross, while current England Under-21 star Steve Sidwell lashed a low shot wide from the edge of the box.
But the best chance fell to Murray four minutes before half-time, when the ball fell invitingly at his feet only for the former Bristol City winger to be denied by a combination of defender Andy Holdsworth and keeper Ian Gray.
Huddersfield started the second half strongly, as defender Steve Yates smashed a header just over the bar from an Andy Holdsworth corner.
But Reading grew stronger as the game wore on, with Sidwell a growing influence.
The home side were also a constant danger down the left wing, with full-back Nicky Shorey and winger John Salako combining well on several occasions.
But it was from the right that Reading made the breakthrough.
Murray had already shot wide and Hughes just failed to get on the end of a Shorey cross as Reading turned the screw in the closing stages.
And their pressure finally told when Hughes opened up the home side with two devilish late crosses.
The first was headed spectacularly wide by substitute Shaun Goater, but the second clinically despatched by top scorer Forster, who headed the ball back across stranded keeper Ian Gray.
Goater came close to doubling the advantage when he combined with Forster before firing a low shot straight at Gray. But a second Reading goal would have been rough on Jackson's side, who worked hard with little reward.