Leyton Orient fell to only their second league defeat of the season as Joe Garner's goal gave Preston victory to knock the hosts off top spot.
The visitors took the lead when Garner struck a wonderful first-time volley beyond keeper Jamie Jones from Keith Keane's cross.
The O's struggled to create and their best chance saw Bailey Wright's last-ditch tackle deny David Mooney.
Garner in the goals
The former Carlisle and Watford striker failed to score in his first 17 Preston games but has now struck four goals in his last three games.
Robbie Simpson forced Declan Rudd into a late save as Preston held on.
Russell Slade's side had scored in all their previous 15 league games and are the Football League's top scorers with 36 but drop to second after Wolves won at struggling Notts County.
Despite becoming the first team to take all three points away from Brisbane Road since February, Preston drop down a place to fifth after Brentford's big win over Crewe.
VIEW FROM THE DRESSING ROOM
Leyton Orient manager Russell Slade told BBC London 94.9:
"It was a tight game. Preston bossed it and made life tough for us in the first half by slowing the game down and dictating the tempo.
"They didn't create a lot either. It was cagey and we grew into it and had a wonderful window of opportunity to equalise late on.
"[Suspended midfielder] Romain Vincelot is the heartbeat of the team and he was missed today.
"We knew today would be tough as they set their stall out and were pretty negative. We are disappointed but are still up there and have the chance for a fine season."
Leyton Orient 01 Jones 02 Omozusi 03 Sawyer (Batt - 62' ) 08 James (Baudry - 70' ) 05 Cuthbert 15 Clarke Booked 11 Odubajo 21 Bartley 10 Mooney (Simpson - 81' ) 09 Lisbie 07 Cox Booked Substitutes 06 Baudry 12 Larkins 14 Batt 17 Vanderhyde 19 Lasimant 22 Stockley 25 Simpson Preston North End 23 Rudd 07 Humphrey (Huntington - 90' ) 03 Laird 06 Wright 22 King 05 Clarke 19 Welsh 02 Keane Booked 09 Davies Booked 14 Garner Booked 12 Gallagher (Kilkenny - 83' ) Substitutes 01 Stuckmann 04 Huntington 11 Holmes 16 Buchanan 17 Monakana 30 Brownhill 37 Kilkenny
Ref: Keith Hill