For how to deal with interference over 1C see here.
Responses to 1C:
1D - 0-7 any distribution (not an A and a K)
1H/S - 8+ pts, 4+ cards;
1nt - 8-11, no 4-card major, balanced or semi-balanced;
2C/D - 8-12 unbalanced, 5+ minor, no 4+ major;
2H - game-forcing with both minors (2nt asks for the longer minor);
2S - puppet to 2nt; either 14+ balanced with no 4-card major or game-forcing minor one-suiter;
2nt - 12-13 balanced, no 4-card major;
3C/D - 5-7, 6+ suit headed by KQ or AQ;
3H/S - 7-card suit headed with 2 top honours and out;
Developement of the auction:
| Hand Type | 11-13 balanced or 4414 | 17-19 balanced, no 5+M | 20-22 balanced, no 5+M |
| Response | |||
| 1D - 0-7 any distribution | bid 1M (showing 3+). Pass on the next round. | Bid 1nt. Further bidding as after 1nt opening. | Bid 2nt. Further bidding as after 2nt opening. |
| 1M - 8+, 4+M | Bid 2M or 1nt (even if opener holds 4sp after a 1H response). Responder can now bid 2C as check-back, 2x/3C as a weak takeout, 2nt as invitational with clubs or 3D/H - invitational 5-5. | Bid 2D (GF showing 17+ balanced or 4 card support). | Bid 2D (GF showing 17+ balanced or 4 card support). Show extra strength later. |
| 1nt - 8-11, no 4-card major, balanced or semi-balanced. | Pass. | Bid 3nt or 2C (shape inquiry showing 17+ balanced or strong with a long minor). | Bid 3nt or 2C (shape inquiry showing 17+ balanced or strong with a long minor) or possibly 4nt (quantative). |
| 2m - 8-12 unbalanced, 5+m, no 4+M. | Pass or bid 2nt/3m (invitational). | Bid 3nt or 4m(forcing). | Bid 4nt or 4m (forcing). |
| 2H- GF with both minors | Bid 3nt or ask for longer minor with 2nt | Bid 4nt or ask for longer minor with 2nt | Bid 5nt or ask with 2nt |
| 2nt - 12-13 balanced,
no 4+M |
Pass or bid 3nt. | Bid 4nt or 3m (could be a 4-card suit) | Bid 4nt or 3m (could be a 4-card suit). |
| 3m - 5-7, 6+ cards to KQ or AQ | Pass or bid 4m (preemptive). | Bid 3nt or 5m. | Bid 3nt, 5m, or more. |
| 3M - 7 card suit with 2 top honours and out. | Pass or bid 3nt/4M. | Do something clever. | Do something clever. |
| Hand Type | 16+, 5+m | 16+, 5+M |
| Response | ||
| 1D - 0-7 any distribution | With a 4-card major bid 1M. Without one bid 2m. With a game-forcing hand bid 3m. After the 2m rebid, responder can bid a new suit at 2-level (4-7, 5+ cards); | Bid 1M (NF) or 2M (Acol 2, forcing). Responder can bid naturally with 4-7. If opener is raised to 2M, bidding goes as after 1M-2M. |
| 1M - 8+, 4+M. | With a 1-suiter and 16-18 bid 3m. With other hands without support bid 2C (GF relay). With support bid 2D (GF) or splinter. | Bid 1/2 other major. This sets up a game-force. With support bid 2D (GF relay) or splinter. |
| 1nt - 8-11, no 4-card major, balanced or semi-balanced. | With diamonds bid 2D, with clubs 2nt. Alternatively bid 3nt (to play), 3m (powerful one-suiter; demand for cue-biding), 4m (RKC Gerber), or 2C (shape inquiry showing 17+ balanced or strong with a long minor). | Bid 2M, game-forcing or 3M (powerful one-suiter; demand for cue-biding). |
| 2m - 8-12, 5+m, unbalanced, no 4+ M. | Bid 2/3 other m (if responder has the wrong one) alternatively double-raise or splinter (after the right one). | Bid 2M. |
| 2H - GF with both minors | Bid 4m (RKC Gerber). | Bid 3M or 2nt asking for longer minor. |
| 2nt - 12-13, balanced, no 4+M | Bid 3m or 4m. Note that 3m might be only a 4-card suit (with 17+ balanced). | Bid 3M. |
| 3m - 5-7, 6+m to KQ/AQ | Do something clever (like pass). | Pass or bid 3M. |
| 3M - 7card suit with 2 top honours and out. | Bid 4m (forcing). | Do something clever. |
Bidding after 1C-1M-2D*:
2H - 5 card (or bad 6) suit bid on the previous round. Opener bids 2nt with a doubleton (further bidding natural); 2S with support (with 11+ responder bids now as after 1M-2nt; with 8-10 and shortness responder bids 2nt and opener may inquiry by bidding 3C).
2S - 4 card suit and 8-10 points. 2nt is a further inquiry: 3m - 5 card minor; 3H - singleton in the other major; 3S - after 1C-1H shows 4 spades and after 1C-1S shows 4432 with a 4 card minor; 3nt shows precisely 4333 after 1C-1S and either 4432 or 4333 after 1C-1H.
2nt - 4M in a balanced hand with 11+ HCP; further bidding is natural; with the support hand opener bids 3M.
3m - 5+m and only 4 card M, 11+ HCP; further bidding is natural; with the support hand opener bids 3M and responder shows a singleton .
3M - good 6+M, no singleton
3 other M/4m - good 6+ M, splinter
Bidding after 1C-1M-2C*:
2C shows either a two-suiter without support for responder's major or a minor one-suiter with 19+ points (minor one-suiter with 16-18 HCP are bid 1C-1M-3m). Now the suits are bid up the line, with the key point that the responder shows a 3-card diamond support. Thus after 1C*-1M-2C*, responder's rebids:
2D - 3+ diamonds; now opener bids 2M with 3-card support, 2OM (other major) with 4 cards in that major, 2nt with clubs (showing either a minor 2-suiter with longer clubs or 19+ with clubs; responder bids 3C with 3-card support), or 3D showing with diamonds.
2H (after 1C-1S) - 4+ hearts, less than 3 diamonds.
2H (after 1C-1H) - 5+ hearts, less than 3 diamonds.
2S(after 1C-1H) - exactly 4 hearts, 4 spades, less
than 3 diamonds (and so at least 3 clubs).
2S(after 1C-1S) - 5+ spades, less than 3 diamonds,
less than 4 hearts (and so either 6 spades or at least 3 clubs).
2nt - 4 cards in the major bid, less than 3 diamonds, less than 4 cards in the other major (and so at least 4 clubs).
3m - 5+ cards, denies 4 cards in the other major and 3 of the other minor.
After 1C-1M-2C-2H/S, 2nt by opener shows clubs.
Responder bids 3C with 3-card support.
Bidding after 1C-1nt-2C* ("Doubleton Stayman"):
2D - no major doubleton; 2H is a further relay: 2S - 3334, 2nt - 3343, 3C - 3325, 3D - 3352.
2H/S - doubleton in the major bid, 3 cards in the other major; 2nt by opener is a further relay. The responder bids 3m with a 5-card suit (thus showing 5-3-3-2 shape) and otherwise (with 4-4 in minors) bids: 3nt with a stopper in the doubleton, 3 of the original doubleton without a stopper and 8-9 pts, 3 of the other major with 10-11 pts (and no stopper in the doubleton).
2nt - doubletons in both majors, i.e. both minors: 2254 or 2245.
3m - 6 cards.
Subsequent bids at 3-level by opener show stoppers if in a major; set trumps and begin cue-bidding if in a minor.
Bidding after 1C-1H-1S:
1nt - 11+ balanced, doubleton spade;
2nt - 11+ balanced with 4-card spade support;
opener bids as after 1S-2nt;
3nt - 8-10 balanced; doubleton spade;
2S - 11+, 3-card spade support;
3S - 8-10, 3-card spade support;
4S - 8-10, 4-card spade support;
4m- splinter with 4-card spade support,;
Strong 4441 hands:
After 1C-1M, 2nt shows 4441 with singleton in partner's suit and 19+ points; 3nt shows the same distribution and 16-18 points.