The Muiderberg convention in the card game Bridge is also known as the Dutch Two opening. It is a preemptive opening based on a two-suiter with precisely a fivecard major and a minor suit (fourcard or longer). In Muiderberg the 2 opening denotes five hearts and an unknown minor suit, whilst 2 denotes five spades and an unknown minor suit.

The partner of the Muiderberg opener can take the following actions:

• pass (with tolerance for the opened suit)
• bid 3 (a pass-or-correct bid)
• bid 3 to invite for game in the major suit
• bid 3/ as balancing
• ask for the minor suit using a 2NT relay bid with a strong hand.

The 2NT response does not have to be game forcing, because bidding game can depend on the color and length of the minor suit. The Muiderberg opener can respond in several ways to the 2NT answer:

• bid 3 with a minimum and clubs / with a four-card clubs
• bid 3 with a minimum and diamonds / with a four-card diamonds
• bid 3 with a maximum and clubs / with a five-card or more clubs
• bid 3 with a maximum and diamonds / with a five-card or more diamonds

Both approaches are equally popular.

This convention is named after the Dutch village Muiderberg, the residence of the designers of this two-level opening (Onno Janssens and Willem Boegem).

Bridge conventions