Main article: 1978 Five Nations Championship
England
Head coach: Peter Colston
- Bill Beaumont (c.)
- Mike Burton
- David Caplan
- Maurice Colclough
- Barrie Corless
- Fran Cotton
- Robin Cowling
- Peter Dixon
- Paul Dodge
- Dusty Hare
- Alastair Hignell
- Nigel Horton
- Charles Kent
- Andy Maxwell
- Bob Mordell
- Tony Neary
- Barry Nelmes
- Alan Old
- Mike Rafter
- John Scott
- Mike Slemen
- Peter Squires
- Peter Wheeler
- Malcolm Young
France
Head coach: Jean Desclaux
- Jean-Michel Aguirre
- Jean-Luc Averous
- Jean-Pierre Bastiat (c.)
- Christian Bélascain
- Roland Bertranne
- Louis Bilbao
- Daniel Bustaffa
- Gérard Cholley
- Jérôme Gallion
- Jean-François Gourdon
- Francis Haget
- Jean-François Imberbon
- Guy Noves
- Alain Paco
- Michel Palmie
- Robert Paparemborde
- Jean-Pierre Rives
- Jean-Claude Skrela
- Bernard Vivies
Ireland
Head coach: Noel Murphy
- Ned Byrne
- Willie Duggan
- Tony Ensor
- Mick Fitzpatrick
- Mike Gibson
- Tom Grace
- Moss Keane
- Alistair McKibbin
- Stewart McKinney
- Freddie McLennan
- Paul McNaughton
- John Moloney (c.)
- Lawrence Moloney
- John O'Driscoll
- Phil Orr
- Fergus Slattery
- Donal Spring
- Harold Steele
- Tony Ward
- Pa Whelan
Scotland
Head coach: Nairn McEwan
- Mike Biggar
- Richard Breakey
- Sandy Carmichael
- Alastair Cranston
- Colin Deans
- Bill Gammell
- David Gray
- Bruce Hay
- Brian Hegarty
- Graham Hogg
- Andy Irvine
- Don Macdonald
- George Mackie
- Duncan Madsen
- Ian McGeechan
- Alastair McHarg
- Ian McLauchlan
- Doug Morgan (c.)
- Norman Pender
- Jim Renwick
- David Shedden
- Alan Tomes
- Ron Wilson
Wales
Head coach: John Dawes
- Phil Bennett (c.)
- Terry Cobner
- Gerald Davies
- Gareth Edwards
- Charlie Faulkner
- Steve Fenwick
- Ray Gravell
- Allan Martin
- Graham Price
- Derek Quinnell
- Jeff Squire
- Geoff Wheel
- J. J. Williams
- J. P. R. Williams
- Bobby Windsor
- Wales used the same 15 players during the competition