If your partner has opened 1♦, his/her distribution could be almost anything. It is very important to find out more about that distribution, and in particular, to see if a fit in a major suit can be found.
The first requirement for a response is to have 6 DP or more for a response at the 1 level, and 10+ DP for a minimum response at the 2 level (except for the 3♦ response). Minimum point requirements are even higher for bidding after an interfering bid.
Responses are classified as responses to with no interference and with interference.
Responses to a 1♦ Opening with no Interference
| Your bid | Requirements | Comments |
| 1♥/1♠ | This is a forcing bid showing a 4+ card major suit. You may also have 4 cards in the other major. | With 4-4 in the majors, bid 1♥ first. With 5-5 or 6-6 in the majors, bid 1♠ with 6-9 DP, and 1♥ with 10+ DP. With two unequal majors (6-5, 7-5, 7-6 or 8-5) bid the longer suit first. |
| 1NT | Denies a 4-card major suit or longer (4+), and promises 5-9 HCP. Should have a balanced or semi-balanced distribution. | |
| 2♣ | Forcing bid, showing 10+ HCP and at least a 4-card (but normally 5+) suit. Denies a 4-card major. | |
| 2♦ | This is a forcing bid showing at least 5 diamonds, and denies a 4+ card major. Promises 9+ HCP. Called an inverted minor single raise. | An excellent way to decide between NT and minor-suit contracts. |
| 2♥/2♠/3♣ | These are all forcing bids (essentially to game). They promise nice 5+ card suits. Minimum points: 16 HCP. | |
| 2NT | Denies a 4-card major suit or longer (4+), and promises 10-11 HCP. Should have a balanced or semi-balanced distribution. | |
| 3♦ | This is a pre-emptive bid, showing 5-card support for diamonds and no more than 8 HCP. Lower point limit is determined by vulnerability. No 4+ card major suit. | A complementary bid to the 2♦ inverted minor raise. |
| 3♥/3♠/4♣ | These are splinter bids, normally forcing to game. The suit bid shows a singleton or void, good 5-card support for diamonds and 13+ HCP. No 4+ card major. | |
| 3NT | The usual bid with 12+ HCP, no 4+ card major and well-distributed points. | |
| 4♦ | Forcing to 5♦ at least. Good 5+ card diamond support, no 4+ card major, 16+ SP and at least 3 MCCs. | A slam try. |
| 4♥/4♠/5♣ | These are essentially pre-emptive bids with a 7+ card suit and 10+ HCP. | With any perceived chance of 3NT (rather than 4♥, 4♠, 5♣ or slam), other bids should be made. |
| 4NT | Blackwood. Very strong try for 6♦ or 6NT. | All you care about is how many Aces opener has. |
| 5♦ | You have the long suit and the points to play a game contract, but no more than 2 MCC. |
Responses to a 1♦ Opening after Interference
| RHO action | Your bid | Requirements | Comments |
| Double | Pass | Generally with 0-7 DP. | See below. |
| Redouble | This bid promises at least one 4-card major, and 8+ DP. Forcing | ||
| 1♥/1♠ | 8+ DP and a 5+ card suit. May have 4 in the other major. Forcing. | You may lie a bit with a nice 5-card suit, and bid it with 5-7 DP. | |
| All other bids | Same as above. | ||
| 1♥/1♠ | Pass | Generally with 0-7 DP. | |
| Double | This forcing bid is the negative double, and generally shows 8+ DP and exactly 4 cards in the unbid major. If RHO bids 1♠, a double can even mean 5 hearts and 8-9 HCP (as you should not go to the 2 level with <10 points). | ||
| 1NT/2NT/3NT | 8-9/10-11/12+ HCP but with some control of opponent's suit at the 1NT level and good control at the 2/3NT level. No 4+ cards in the unbid major. | ||
| Cue-bid (e.g. 2♥ over 1♥) | Shows a very strong hand (13+ SP) with 5+ diamond support and shortness in or strong control of the opponent's suit. Forcing. | ||
| Other bids | Same as above | ||
| 1NT | Pass | Generally with 0-9 DP. | |
| Double | For penalties. | ||
| 2♣/2♥/2♠ | 8+ DP, with 5-card suit. | ||
| 2♦ | 5-8 DP, with 5-card support. | ||
| 2NT/3NT | 10-11/12+ HCP. No 4-card major. | You are a brave player! | |
| 3♦ | 9+ DP, with 5-card support. | ||
| Other bids | Same as above | ||
| 2♣ | Pass | Generally with 0-7 DP. | |
| Double | This is the "negative double", showing 10+ DP and asking for a 4-card major. Forcing. | ||
| 2♦ | 5-8 DP, with 5-card support. | ||
| 2♥/2♠ | 8+ DP, with 5-card suit. | ||
| 2NT/3NT | 10-11/12+ HCP, with some control of clubs. No 4-card major. | ||
| 3♣ | Cue-bid showing a strong hand with 5+ diamond support and singleton or void in clubs. Forcing. | ||
| 3♦ | 9+ DP, with 5-card support. | ||
| Most other bids | Same as above | ||
| Interference bids above 2♣ | Pass | If you are not strong enough to bid something or double. | |
| Double | (a) At the 2- and 3-level this promises 10+ DP and an unbid 4-card major. | ||
| Diamond bids | Bid your strength if you can, otherwise pass or double. You should have 5+ diamonds and 10-12 SP for 3♦, 13-14 for 4♦ and 15+ for 5♦. | ||
| Cue-bid (e.g. 1♦ - 2♥ - 3♥) | Shows a strong hand with either 5+ diamond support or a biddable long suit. Forcing. | ||
| New suit at minimum level | 5-card suit and enough strength to bid at the level required. Unless already at game, forcing. | ||
| New suit with jump shift | 5-card suit and wishing to show extra strength. Unless already at game, forcing. | ||
| NT bids | Enough strength to bid at the level required. Opponent's suit is controlled. |
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