Kroll is a compact way to solve an awkward major-suit-raise problem: responder has invitational values, exactly three-card support, and no desire to force to game.
The convention is named after Dan Kroll, who plays in the Quicktricks Bridge Club in San Francisco, California. In a partnership that plays Kroll, the auction starts with an uninterrupted 1♥ or 1♠ opening, then responder bids 3♣ artificially.
The Basic Agreement
After partner opens one of a major and there is no interference:
1♥ 3♣or
1♠ 3♣Responder’s 3♣ is Kroll. It shows:
- Limit-raise strength, roughly 10-12 support points
- Exactly three cards in opener’s major
- Not enough strength for a game force
- A hand that wants opener to judge game, not a natural club suit
That last point matters. 3♣ is artificial. It says, “Partner, I have a real raise, but only three trumps.”
Why Kroll Exists
Standard methods leave three-card invitational raises a little clumsy.
A direct jump raise, such as 1♠-3♠, often promises four-card support. Bergen-style methods also use 3♣ or 3♦ for four-card raises. Jacoby 2NT is too strong, because it is game-forcing. A simple raise to 2♠ can undersell a good 11-count.
Kroll gives the partnership one exact box for this hand type: invitational, major-suit support, exactly three trumps.
Opener’s 3♦ Ask
After Kroll, opener can bid 3♦ as an asking bid:
1♠ 3♣
3♦ ?Responder now clarifies the hand.
Responder’s Rebids After 3♦
Responder has three kinds of answers.
Three of the Major: I Do Not Like My Hand
1♠ 3♣
3♦ 3♠Bidding three of opener’s major says the hand is on the low side or poorly fitting. It is a sign-off. Responder still has the promised limit raise with exactly three trumps, but the hand does not have extras.
Typical reasons to sign off:
- Minimum values for the range
- Scattered queens and jacks
- No useful shortness
- Poor controls
- Soft values in side suits
Four of the Major: I Like My Hand
1♥ 3♣
3♦ 4♥Bidding game says responder likes the hand. The values are still invitational rather than game-forcing in the original description, but opposite opener’s interest, responder is happy to accept.
Typical reasons to bid game:
- Maximum values for the range
- Strong trumps for only three-card support
- Aces and kings rather than queens and jacks
- Useful shortness
- Good fit with opener’s likely shape
Any Other Suit: First- or Second-Round Control
If responder bids a suit other than opener’s major, that bid shows a first- or second-round control in that suit. This follows the same idea as Italian-style cue bidding: ace, king, void, or singleton, depending on partnership style.
Examples:
1♠ 3♣
3♦ 3♥Responder shows a heart control.
1♥ 3♣
3♦ 3♠Responder shows a spade control.
1♠ 3♣
3♦ 4♣Responder shows a club control. The original 3♣ was artificial, so this later 4♣ is not showing a club suit. It is a control bid.
Example Hand
Partner opens 1♠ and you hold:
♠ K 8 4
♥ A 7 5
♦ Q 9 6 2
♣ J 8 3You have 10 high-card points, exactly three spades, and enough support to invite game. If Kroll is on, bid 3♣.
If partner asks with 3♦, you probably bid 3♠. The hand is minimum, flat, and full of soft values. You made your invitation, and opener can still continue with extras.
Now change the hand slightly:
♠ K Q 4
♥ A 7 5 2
♦ 9 6 2
♣ K 8 3Same 12 high-card points, exactly three spades, but much better controls and trump texture. After 1♠-3♣-3♦, bidding 4♠ is reasonable.
Kroll Compared with Bergen Raises
Kroll and Bergen Raises both use artificial 3-level responses after a one-major opening, so partnership clarity is essential.
A common Bergen structure is:
- 3♣: Limit raise with four-card support
- 3♦: Constructive raise with four-card support
- 3 of the major: Weak/preemptive raise
Kroll changes the meaning of 3♣. Instead of showing four-card support, it shows exactly three-card support and invitational values.
That means you need another agreement for four-card limit raises. Some pairs keep a direct jump to three of the major for four-card limit raises. Others use a different Bergen-style structure. The important thing is not the label. It is that both partners know which raises show three trumps and which show four.
Alerting and Partnership Notes
Kroll is artificial and should be disclosed according to your local alert rules. Do not assume opponents will understand that 3♣ is not clubs.
Agree on these details before using it:
- Whether the range is 10-12 high-card points or 10-12 support points
- Whether 3♦ is always an ask or only with game interest
- Whether control bids after 3♦ show first-round controls only or first- and second-round controls
- What direct three-of-the-major means when Kroll is available
- Whether Kroll is off by a passed hand
- Whether Kroll is off after a double or overcall
Technical Bridge Check
The auction is legal and coherent. 3♣ is a legal response after 1♥ or 1♠. Playing it as artificial is a partnership agreement. The stated meaning, limit-raise values with exactly three-card support, fits normal major-raise theory because opener has at least five cards in a standard five-card-major system, producing at least an eight-card fit.
The 3♦ asking bid is also legal. Responder’s sign-off in three of the major, raise to four of the major, or control-showing call in another suit all fit standard constructive bidding logic. Control bids after a fit is known can sensibly show first- or second-round controls, matching Italian-style cue-bidding agreements.
The key partnership constraint is interference. Kroll should be treated as on only after an uninterrupted one-major opening unless both partners explicitly agree otherwise.
Bottom Line
Kroll gives responder a clean way to say: “I have a limit raise, but exactly three trumps.” Opener can place the contract, ask with 3♦, or investigate higher when the fit and controls look good.
It is a small convention, but that is the point. It names one common hand type accurately, and it keeps your major-suit raises from blurring three-card and four-card support.