Peter Stringer, Denis Leamy, Tom Court and Mick O’Driscoll join Ulster hooker Best in the party after helping Ireland win the RBS Six Nations.
Head coach Declan Kidney has selected 12 uncapped players for the series against Canada in Vancouver on May 23 and Eddie O’Sullivan’s USA in Santa Clara, California, eight days later.
Leinster’s qualification for the Heineken Cup final against Leicester, which takes place on the same day as the first Test against Canada, means none of their players have been considered.
Ireland are also supplying 13 members of the Lions squad to South Africa while several veterans – among them John Hayes and Geordan Murphy – are rested.
Bob Casey heads a three-strong Guinness Premiership contingent which includes Leinster-bound Wasp Eoin Reddan and Harlequins prop Mike Ross.
Kidney said: “When we confirmed the tour back in January we knew some of the provinces would be involved in European finals and that we’d also be without any players selected by the Lions.
“We thus felt that it would be a chance to work closely with a larger pool than we would normally do during the season and for players to come through at this level.
“We are continuing to try and build a squad and this tour is a real chance for guys to stake a claim for the November internationals and next year’s Six Nations. We obviously want to win both games but it’s a balancing act trying to do that while exposing players and new combinations to Test level.”
Kidney will fill the one outstanding berth in the squad once the final round of Magners League action is completed.
Connacht’s John Muldoon will captain the Ireland ‘A’ squad in the Churchill Cup, which starts 10 days after the USA match and which is also being overseen by Kidney.
The 27-strong party features players from Leinster, including outside half Jonathon Sexton, while Northampton’s Neil Best must settle for a place among the second string.
“We will be playing Canada for the third time in 12 months with a different team, and we also play Georgia, whom Ireland met in the last World Cup, so it should be very good exposure for the players to test level rugby,” said Kidney.
IRELAND TOUR SQUAD (25): R. Best (Ulster) captain; T. Buckley (Munster), R. Caldwell (Ulster), B. Casey (London Irish), D. Cave (Ulster), T. Court (Ulster), S. Cronin (Connacht), I. Dowling (Munster), G. Duffy (Connacht), C. Henry (Ulster), D. Hurley (Munster), I. Keatley (Connacht), D. Leamy (Munster), K. Matthews (Connacht), J. Muldoon (Connacht), B. Murphy (Munster), N. O’Connor (Ulster), M. O’Driscoll (Munster), E. Reddan (London Wasps), N. Ronan (Munster), M. Ross (Harlequins), D. Ryan (Munster), P. Stringer (Munster), B. Young (Ulster), A. N. Other.
IRELAND A CHURCHILL CUP SQUAD (27): J. Andress (Exeter), N. Best (Northampton), I. Boss (Ulster), T. Buckley (Munster), F. Carr (Connacht), S. Cronin (Connacht), J. Downey (Northampton), D. Fogarty (Munster), C. Healy (Leinster), C. Henry (Ulster), T. Hogan (Leinster), D. Hurley (Munster), F. Jones (Leinster), S. Keogh (Leinster), K. Matthews (Connacht), F. McFadden (Leinster), J. Muldoon (Connacht) captain), F. Murphy (Connacht), J. Murphy (Leicester), S. O’Brien (Leinster), N. O’Connor (Ulster), E. O’Donoghue (Ulster), N. Ronan (Munster), D. Ryan (Munster), J. Sexton (Leinster), D. Toner (Leinster), B. Young (Ulster).