Down advanced to the next round of All-Ireland SFC qualifiers following a facile victory at Pairc Esler in Newry where they ran out decisive winners by 4-18 to 0-09.
James McCartan's side laid the foundation for victory with first-half goals from Conor Laverty and Niall Madine which helped them to a 2-10 to 0-4 interval lead.
Leitrim, who had to make seven changes from the side that lost to Roscommon in the Connacht championship, did not help their cause with basic defensive errors.
Down were ruthless from start to finish, with all six forwards finding the target before the interval.
Laverty, who finished with 2-04, got his first goal after nine minutes when an effort from Mark Poland came back off an upright.
Madine punished Leitrim with another when they failed to clear their lines and he made no mistake from close range.
Leitrim’s hopes of getting back into the game were dashed approaching half-time when Down goalkeeper Michael Cunningham did superbly to tip over an effort from Robbie Lowe.
Laverty then got his second when he fisted home after 42 minutes following another good passing move by a rampant Down side.
Leitrim, as always, battled away but struggled to get back into contention and had to be content with points from Emlyn Mulligan and Gary Reynolds.
The Mourne men picked off scores at will and the rout was completed when substitute Damien Turley found the net going into the final quarter as Down eased their way to a 21-point victory, their biggest ever in the qualifiers.
Down: M Cunningham (0-01, 0-01 ’45); D O’Hagan, N Donnelly, D McCartan; K McKernan (0-01), C Garvey, C McCartan; D Gordon (0-01), P Turley; B Coulter (0-02), C Maginn (0-01), M Poland (0-02); D O’Hare (0-04, 0-03f), N Madine (1-00), C Laverty (2-04).
Subs: L Doyle (0-02, 0-02f) for O’Hare (40 mins), C Toner for P Turley (43 mins), E McCartan for Madine (44 mins), D Turley (1-00) for Coulter (50 mins), O Costello for D McCartan (51 mins), A Carr for Garvey (55 mins).
Leitrim: P Farrelly; A Wynne, D Wrynn, B McWeeney; B Prior, Gary Reynolds (0-01), S McWeeney (0-01); D Sweeney, D Moran; A McLoughlin, E Mulligan (0-05, 0-04f), G Hickey; R Cox, R Lowe (0-01), K Conlon.
Subs: F Clancy for McLoughlin (35 mins), M McWeeney for Moran (44 mins), N Moore (0-01) for Lowe (57 mins) C Conlon for Cox (58 mins), A Hickey for G Hickey (64 mins).
Referee: A Nolan (Wicklow).