Michael Dunlop and Guy Martin are confirmed starters for the Cookstown 100 road races on 26 and 27 April.
Dunlop will ride Honda machinery in the Open, Supersport and 250cc races and a Kawasaki bike in the Supertwins under the banner of his own MD Racing team.
Martin has become a regular at the Orritor circuit in recent years and will again ride for the Tyco Suzuki outfit, based at nearby Moneymore.
William Dunlop has entered the Open, 600cc, feature and 125cc events.
The elder of the Dunlop brothers is set to compete on the CD Racing 600cc Yamaha which he will campaign at selected national road races this season.
The 27-year-old is riding for the Milwaukee Yamaha team in the British Supersport series this year, but the Cookstown does not clash with any round of that championship.
Michael Dunlop has already carried out extensive testing on the Honda TT Legends Superbike which he will ride at the North West 200 and Isle of Man TT and will be part of that team's squad for the opening World Endurance round at Bol d'Or a week before the Irish national roads season gets underway.
The 24-year-old will ride a Hunts/McAdoo Fireblade in the Open class at Cookstown.
Martin will warm up for the County Tyrone event by racing at the Scarborough Spring National Cup on 21 April.
The colourful Lincolnshire lad won the Cookstown 100 Open race last year in controversial circumstances as Ryan Farquhar accused him of overtaking under a yellow flag.
Among the other notable entries for Cookstown are English rider rider Dean Harrison, who will make his debut at the circuit, and KMR Kawasaki pairing Jamie Hamilton and Brian McCormack.
Enkalon Trophy winner Derek Sheils will continue the build-up to his TT debut by taking in the feature and Open events, while Ballygowan rider Michael Pearson should also be a leading contender.
Saintfield's Davy Morgan, Michael Sweeney and Wayne Kirwan should challenge for honours while Czech rider Michael Dokoupil and Portugal newcomer Nuno Caetano head the international entry.
The meeting will feature 18 races, three after Friday's practice sessions and 15 on Saturday.
Roads close at 12:00 BST on Friday and 10:00 on Saturday.