Singapore Contract Bridge Association
Raffles Junior College
by
Dr Wong Choo Wai
NATURAL BIDDING SYSTEM
General Principles
1. Priority of game contracts: 4♥/♠ (26+ HCPs), 3NT (26+ HCPs), 5♣/♦ (29+ HCPs)
2. Aim for fit between partners of at least 8 cards in trump suit
3. After a 1-level suit opening, responses or rebids of new suits by responder are forcing (as game
cannot be excluded)
4. Conventional bids (= bids that do not promise the suit bid) must be alerted e.g. 2♣ opening
5. Ranges of HCPs: 0-5, 6-9, 10-12, 13-15, 16-18, 19-21, 22+.
6. Responses of new suit at 1-level promises 6+ HCPs, 4+cards; 2-level promises 10+ HCPs, 5+ cards.
Opening Bids
Opening Bids HCPs No. of cards in suit bid Description
1♣/♦ 12 – 21 3+ Rebid 2NT=18-19 HCP, balanced
1♥/♠ 12 – 21 5+
1NT 15 – 17 Balanced 4333, 4432 or 5332 (5-card minor)
2♣ 22+ 0 Any distribution, conventional (artificial) bid
2♦/♥/♠ 0 – 11 6+ Weak
2NT 20 – 21 Balanced 4333, 4432 or 5332
3♣/♦/♥/♠ 0 – 12 7+ Pre-emptive bid
3NT 9 – 15 Solid 7+card minor with no outside King or
Ace
4♣/♦/♥/♠ 0 – 12 8+ Pre-emptive bid
Responses to 1♣ (3+ cards, 12-21 HCPs)
Responses HCPs No. of cards in suit bid Description
1♦/♥/♠ 6+ 4+ Bid longest suit first, bid up the line if all 4
cards, F1
1NT 6-9 Denies 4-card ♦/♥/♠
2♣ 6-9 5+ Denies 4-card ♦/♥/♠
2♦/♥/♠ 0-7 6+ Weak, pre-emptive
2NT 10 -12 Denies 4-card ♦/♥/♠
3♣ 10 -12 5+ Denies 4-card ♦/♥/♠
3♦/♥/♠ 0-7 7+ Weak, pre-emptive
3NT 13 - 15 Denies 4-card ♦/♥/♠
4♣ 13 - 15 5+ Denies 4-card ♦/♥/♠
5♣ 16 - 18 5+ Denies 4-card ♦/♥/♠
1
Responses to 1♦ (3+ cards, 12-21 HCPs)
Responses HCPs No. of cards in suit bid Description
1♥/♠ 6+ 4+ Bid longer suit 1st, or up the line if both 4
cards, F1
1NT 6-9 Denies 4-card ♥/♠
2♣ 10+ 5+ Forcing till 2NT (F2NT)
2♦ 6-9 5+ Denies 4-card ♥/♠
2♥/♠ 0-7 6+ Weak, pre-emptive
2NT 10 -12 Denies 4-card ♥/♠
3♦ 10 -12 5+ Denies 4-card ♥/♠
3♣/♥/♠ 0-7 7+ Weak, pre-emptive
3NT 13 - 15 Denies 4-card ♥/♠
4♦ 13 - 15 5+ Denies 4-card ♥/♠
5♦ 16 - 18 5+ Denies 4-card ♥/♠
Responses to 1♥(5+ cards, 12-21 HCPs)
Responses HCPs No. of cards in suit bid Description
1♠ 6+ 4+ F1
1NT 6-9 Denies 4-card ♠
2♣/♦ 10+ 5+ Forcing till 2NT (F2NT)
2♥ 6-9 3+
2♠ 0-7 6+ Weak, pre-emptive
2NT 10 -12 Denies 4-card ♠
3♥ 10 -12 3+ Denies 4-card ♠ & 5-card minor
3♣/♦/♠ 0-7 7+ Weak, pre-emptive
3NT 13 - 15 Denies 4-card ♠
4♥ 13 - 15 3+ Denies 4-card ♠ & 5-card minor
Responses to 1♠ (5+ cards, 12-21 HCPs)
Responses HCPs No. of cards in suit bid Description
1NT 6-9 Denies ♠ support
2♣/♦/♥ 10+ 5+ Forcing till 2NT (F2NT)
2♠ 6-9 3+
2NT 10 -12 Denies ♠ support
3♣/♦/♥ 0-7 7+ Weak, pre-emptive
3♠ 10 -12 3+ Denies other 5-card suit
3NT 13 - 15 Denies 4-card ♠
4♠ 13 - 15 3+ Denies other 5-card suit
2
Responses to 1NT (15-17 HCPs, 4333 or 4432 or 5332)
Responses HCPs No. of cards in suit Description
2♣ 8+ Stayman convention asking opener to rebid:
2♦ = no 4-card major
2♥ = 4-card ♥ (or 4-card♥+ 4-card♠)
2♠ = 4-card♠ only
2♦ 0+ Jacoby transfer asking opener to rebid 2♥.
Promises 5+card ♥.
After 1NT: 2♦, 2♥, responder rebids:
Pass = 0-8 HCPs, 5+card ♥, to play
2NT = 9-10 HCPs, invitational, 5-card ♥
3♥ = 9-10 HCPs, nvitational, 6+card ♥
3NT = 11-15 HCPs, 5-card ♥
4♥ = 11-15 HCPs, 6+card ♥
2♥ 0+ Jacoby transfer asking opener to rebid 2♠.
Promises 5+card ♠
After 1NT: 2♥, 2♠, responder rebids:
Pass = 0-8 HCPs, 5+card ♠, to play
2NT = 9-10 HCPs, invitational, 5-card ♠
3♠ = 9-10 HCPs, nvitational, 6+card ♠
3NT = 11-15 HCPs, 5-card ♠
4♠ = 11-15 HCPs, 6+card ♠
2♠ 10+ Minor Suit Stayman convention (with slam
interest) asking opener to rebid:
2NT = no 4-card major
3♣ = 4+card ♣ (or 4-4 minors)
3♦ = 4+card ♦
2NT 9 – 10 Denies 4-card major, invitational to game
3♣/♦ 5-8 6+ Invitation to 3NT if opener has 1 honour in suit or
3-cards, otherwise pass Suit quality > KQxxxx
3♥/♠ 9+ 4-4-4-1 with singleton in suit bid
3NT 11 - 15 Denies 4-card major, to play
4♣ 13+ any distribution Gerber convention asking opener to rebid:
4♦ = 0 or 4 aces
4♥ = 1 ace
4♠ = 2 aces
4NT = 3 aces
4NT 16 - 17 Denies 4-card major, invitational to 6NT
5NT 20 - 21 Denies 4-card major, invitational to 7NT
6NT 18 – 19 To play; opener must pass
3
Responses to 2♣ (22+ HCPs, any distributiuon)
Responses HCPs No. of cards in suit bid Description
2♦ 0–6 any distribution Negative response, opener rebids:
2♥/♠ = 5+ cards
2NT = 22-24 HCPs, balanced
3♣/♦ = 5+ cards
2♥/♠ 7+ 5+ At least 1 honour in suit bid (A/K/Q)
2NT 7 - 10 Denies good suit
3♣/♦ 7+ 5+ 5-card with 2 honour, or 6+cards with 1 honour
Overcalls
Overcall HCPs No. of cards in suit bid Description
1-level (1♦- 8 – 17 5+ 8+ with good suit, 10+ with poorer suit
1♥*) Suit must be at least K9xxx
2-level (1♠- 10 – 17 5+ 10+ with 6-card suit, 12+ with 5-card suit
2♥*) Suit must be at least KJTxx
3-level (2♠- 12 – 17 5+ 12+ with 6-card suit, 10+ with 5-card suit
3♥*) Suit must be at least KJTxx
Jump (1♠- 5 – 11 6+ Weak, Suit must be at least KJTxxx, Must not
3♥*) have two Aces
Double 12+ 2 or less Takeout double, at least Jxx in all outside suits
X-and-rebid 18+ or 5 or 6+ Double-and-rebid, very strong hand
16+
Advances to one-level Overcall (e.g. 1♦-1♥*)
Advances HCPs No. of cards in suit bid Description
2♥ 5–9 3+ Competitive, non-forcing (NF)
1♠/2♣ 5 – 11 5+ At most singleton ♥, NF
1NT 8 – 10 Stoppers in all outside suits, especially ♦
2♦ 12+ 0+ Cuebid, F1. Will usually have 5-card suit with
12+ HCP and no support for ♥.
2NT 11 – 13 Stoppers in all outside suits, invitational
3♦ 10+ 0+ Invite to game in ♥, 3-card ♥ or better
3♥ 5–9 4 Competitive, NF
3NT 14+ Stoppers, usually with ♥ fit. NF
4♥ 5–9 5+ Pre-emptive, NF
4NT Blackwood
4
Advances to two-level Overcall (e.g. 1♠-2♥*)
Advances HCPs No. of cards in suit bid Description
2♠ 12+ 0+ Cuebid, FG. Will usually have 5-card suit with
12+ HCP and no support for ♥
2NT 11 – 12 Stoppers in all outside suits, invitational
3♣/3♦ 5 – 11 5+ At most singleton ♥, NF
3♥ 5–9 3+ Competitive, NF
3♠ 12+ 0+ Forcing to game in ♥, 3-card ♥ or better
3NT 13+ Stoppers, usually with ♥ fit, NF
4♥ 5–9 4+ Competitive, NF
4NT Blackwood
Advances to three-level Overcall (e.g. 2♠-3♥*)
Advances HCPs No. of cards in suit bid Description
3♠ 12+ 0+ Cuebid, FG. 5-card suit with 12+ HCP and no
support for ♥ or forcing to game in ♥
3NT 13+ Stoppers, usually with ♥ fit, NF
4♣/4♦ 5–9 5+ At most singleton ♥, NF
4♥ 5–9 4+ To play (maybe strong, maybe weak), NF
4NT Blackwood
