Chris Wood netted his ninth goal of the season to give Millwall a slender half-time lead over Brighton & Hove Albion at The Amex this evening.
Playoff contenders Millwall were out of the blocks quickly, with Seagulls stopper Tomasz Kuszczak keeping out a Liam Trotter header inside the first minute.
Brighton's best chance of the opening quarter of an hour came when Will Buckley rose to meet David Lopez's corner but headed wide of the upright.
The visitors then took the lead in the 25th minute when James Henry picked out Shane Lowry on the left and the full-back crossed for the in-form Wood to flick home at the near post.
Gus Poyet's side responded well to going behind and came within inches of levelling when skipper Gordon Greer's header came back off the angle of post and crossbar.
Trotter almost doubled the Lions' lead but couldn't find the target with a free header four minutes before the interval.
Victory for Millwall would see them rise above Leicester to fifth place in the Championship.