Basic Niemijer

/2NT: B, 20-22. Could be a 5422, or even single A or K.

- 3♣: 4+, asks for 4-M and 5-M (replaces Stayman)

/ 3♦: unknown 4-M (or even 4-4-M)

- 3♥: 4-♠ INV! Opener chooses end contract (3NT or 4♠).

- 3♠: 4-♥ INV! Opener chooses end contract (3NT or 4♥).

- 3NT: to play (answerer probably has a 5-M and was hoping for a 5-M at partner)

- 4♥: 4-♥ and 4-♠. Opener chooses, and is certain there's a fit.

/ 3♥: 5-♥

/ 3♠: 5-♠

/ 3NT: no 4-♥ or 4-♠

- 3♦♥: Jacoby transfers, 0+, analogous classical /1NT opening

- 3♠: transfer for ♣, interested in slam

/ 3NT: reject, to play

/ 4♣: RKC♣

- 3NT: to play

- 4♣: transfer for ♦, interested in slam

Extended Niemeijer

after /3♦NT like above, add:

- 4♣: Minor Suit Ask

/ 4♦: length in m (5-m after initial /3NT or 4-m after initial /3♦ rebid)

- 4♥: which m?

/ 4♠: 5/4-♣

/ 4NT: 5/4-♦

/ 4♥: 4/3-♣

/ 4♠: 4/3-♦

/ 4NT: same length in both m 4/3-♣♦