1NT

Opener has one of 2 classes of hands:

Responses

There are 2 artificial responses (one game forcing) which require opener to clarify the nature of his hand, and a number of natural bids for balanced and single-suited hands.

2C
Forcing

An artificial inquiry, showing 8-11HCP.

Opener's rebid may show that he has a strong hand (16-17HCP), or a weak hand (3-3 in the majors, 4-5 Clubs, 13-15HCP).

Over a strong rebid responder may make a further relay, enquiring about shape; over a weak rebid responder can sign off or bid 3 of a major, requiring opener to choose between game in the major or in NT.

Opener's rebids are as follows:

2D
3-3-2-5 with 13HCP, or 3-3-3-4 with 13-14HCP

Responses through to 3S:

Pass,2H,2S,2NT,3C,3NT
To play
3D
Shows Diamonds; opener bids 3NT with any of the top 3 honours.
3H,3S
Forcing

Opener chooses between game in NT or in the named suit.

2H
3-3-2-5 with 14HCP, or 3-3-3-4 with 15HCP

Responses through to 3S:

Pass,2S,2NT,3C,3D,3NT
To play
3H,3S
Forcing

Opener chooses between game in NT or in the named suit.

2S
16-17HCP balanced.

Responses:

Pass,3C,3D,3NT
To play
2NT
Further relay; opener rebids
3C
No 4card major
3D
4-4 in the majors, 3 Diamonds
3H
4 Hearts, not 4 Spades.
3S
4 Spades, not 4 Hearts.
3NT
4-4 in the majors, 3 Clubs
3H,3S
Forcing

Opener chooses between game in NT or in the named suit.

2NT
3-3-2-5 with 15HCP

Responses through to 3S:

Pass,3C,3D,3NT
To play
3H,3S
Forcing

Opener chooses between game in NT or in the named suit.

2D
Forcing to Game

An artificial inquiry, showing 12+HCP.

Opener rebids as follows:

2H
16-17HCP, 4+ Hearts

Responder may relay with 2S or 2NT; raise opener's suit; bid game; or introduce a new suit (other than with 2S). A new suit from opener (other than in response to a relay) is a cue bid, agreeing trumps.

2S is a relay showing a spade suit, and 2NT is a relay that doesn't; opener bids a second suit if he has one, repeats Hearts to show 5, or rebids in NT.

2S
16-17HCP, 4+ Spades, denies 4 Hearts.

Responder may relay with 2NT; raise opener's suit; bid game; or introduce a new suit. A new suit from opener (other than in response to a relay) is a cue bid, agreeing trumps.

2NT is a relay; opener bids a second suit if he has one, repeats Spades to show 5, or rebids in NT.

2NT
13-15HCP

Responses:

3C
Conventional relay. Opener rebids:
3D
13-14HCP, 3-3-3-4
3H
15HCP, 3-3-3-4
3S
13-14HCP, 3-3-2-5
3NT
15HCP, 3-3-2-5

Responder then bids game, or starts cue bidding.

3D,3H,3S
Opener shows fit and strength by bidding 3NT, raising or cue bidding.
3C
16-17HCP, no 4card major.

Responder can make a minor suit enquiry with 3D; sign off with 3D; bid 3H or 3S with a moderate suit (opener can raise or cue bid to agree suit); or bid at the 4 level to show a strong, 6 card suit (forcing): opener cue bids, or bids 4NT to deny slam interest.

Responses to 3D relay:

3H
3-3-3-4 (4 Clubs)
3S
3-3-4-3 (4 Diamonds)
3NT
4-4 in the minors
4C
5 Clubs
4D
5 Diamonds
2H
Weak hand, 5+ Hearts.
2S
Weak hand, 5+ Spades.
2NT
9-10HCP, no interest in the majors.
3C,3D,3H,3S
6card suit headed by two of the top three honours and a maximum of 6-7HCP.
3NT
12+HCP, no interest in the majors or slam.
4C
Forcing

Transfer to 4H

4D
Forcing

Transfer to 4S

Interference

Jumps to 3 retain their character.

Double by responder is a non-forcing inquiry, and 2NT is a game-forcing inquiry

If opener has a 16-17HCP hand it is his duty to tell partner by doubling, or in response to the relay.

Rebidding after Responder's Double
Pass
Transforming into a penalty double.
2NT
13-15HCP, denies 5 Clubs.
3C
13-15HCP, 5 Clubs.
Major
16-17, 4card major
Cue Bid
16-17, no guard and no major
3NT
16-17, a guard in opponent's suit.
Rebidding after Responder's 2NT Relay

With 13-15HCP, opener rebids 3C; with a strong hand, opener starts bidding his 4 card suits upwards (3NT is Clubs is his only suit), in the style of the Baron convention, until a fit is found or 3NT is reached.