John Anderson scored 74 as Merrion beat Phoenix in the battle of the unbeaten teams. The former Irish international's knock included 9 fours and 3 sixes, from just 59 balls.
He shared stands of 77 in 9 overs with Michael Lewis (39) and 68 in six overs with Max Sorensen (25) as Merrion posted the days highest total of 172 for 4.
Phoenix were never in contention in the reply, limping to just 60 with James Maginnis top scoring with 22 - Aaron Cawley not batting after being injured while bowling.
Skipper Tom Stanton took the bowling honours with 3 for 6.
Saqib Bahadur inspired Leinster to a 66-run victory over North Kildare. He hit 37 and followed it up with four wickets as Kildare were out for 88 chasing 154.
Monil Patel (38) and Tristan de Beer (2-8) were others worthy of mention for Leinster, while for The Maws side Mudassar Aziz clubbed four sixes in a breezy 28.
Highest scoring contest of the day saw Terenure post 169 against Balbriggan.
Irish youth international Seamus Lynch showed his power and potential in the days top score of 84 - taking just 53 balls, and including 10 fours and 4 sixes.
His third wicket stand of 76 in 7 overs with Mick Cotter (47) proving decisive.
Balbriggan kept losing wickets at crucial stages, with Farooq Nasr (34) top scorer in their 143 for 0 - three wickets for Zubair Khan and Sadiq Safi.
Pembroke beat Rush by 45 runs at Sydney Parade defending 126. Ryan Hopkins (23) and Gavin Hoey (21) the best of what looked a modest 126 - three wickets for Nathan McGuire.
However Rush tumbled from 39 for 1 to 81 all out as Scott Ruttle took three wickets and two apiece for skipper Fiachra Tucker, Bill Whaley and Ryan Hopkins.
Robert Forrest's 71 from 53 balls was the catalyst for Clontarf's 27-run win against The Hills.
He added 79 in 12 overs with captain Andrew Poynter (24) as Clontarf made 137 for 4.
Cormac McLoughlin-Gavin made a fluent 34 at the top of the order in the chase, but two wickers apiece for Ehtesham Ahmed, Conor Kelly, Ben McCabe and David Vincent restricted them to 110.
Defending T20 champions Malahide held on to beat Railway Union by 13 runs in a tense contest.
Alistair Frost (32) and Greg Ford (29) the best of their total of 113 for 7.
With Glenn Querl (42) going well in the reply, Railway looked on course for the win, but his dismissal by Cameron Shoebridge (4-19) proved decisive as they finished on 100 for 6.
The only team to chase successfully were YMCA, who beat North County by five wickets at Claremont Road.
Salman Aziz (36) and Eddie Richardson (26) shared a run-a-ball stand of 59 as County posted 117 for 6 - three wickets for Tom Anders.
An opening stand of 54 between Mitchell Thompson (34) and Jack Tector (20) ensured YM were always in control of the chase, with Tim Tector making certain as he hit 3 sixes and 3 fours in a 21-ball unbeaten 43, sealing the win with seven balls to spare.