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Dear Ed en Peter,

My partner opens 1NT, 15-17 HCP. My question is how to respond with these four different types of hands.
1. 10 HCP and 5-4 in spades and hearts.
2. 10 HCP and 4-5 in spades and hearts.
3. 5 HCP and 5-4 in spades and hearts.
4. 5 HCP and 4-5 in spades and hearts.
Let's suppose that partner, the 1NT opener, has three-card suits in both major suits.
What are the standard bidding sequences in these four cases?

Kind bridge-regards,
Jan Goesten

 Answer Ed Hoogenkamp (South)

Dear Jan,

In principle you can show 5-4 in the majors in three ways. Which sequence shows which strength, is a matter of partnership agreement.

I assume you play the most popular type of Stayman, which is the non-forcing Stayman, also known as alternative (as opposed to classical) or weak Stayman. In the UK and the USA it is known as crawling Stayman as well. Just to give a few names!
Since you assume the 1NT opener to have 3-3 in the majors, he will respond 2♦:

Above South shows a weak hand (0-7 HCP) and 4-5 in spades and hearts.

The difference with hands with 5-4 in the majors is, that after applying Stayman with this 4-4-5-0 hand, you pass any of the 1NT opener's responses; also 2♦.

Now to hands with invitational strength (8-9 HCP) and 5-4 in the majors:

Above South bids invitationally (8-9 HCP) with 4-5 in spades and hearts. (Note Peter van der Linden: not so if you play Smolen transfers, see the last part of my answer, below Ed's).

With even stronger (meaning: game-forcing) hands, South doesn't begin with Stayman but with a transfer:

Above South's bidding is game forcing (10⁺ HCP) with 4-5 in spades and hearts.

This is an important principle: if the responder to 1NT applies a Jacoby-transfers first and bids a new suit afterwards, that sequence is game forcing.
I have limited my answer to your actual question. If you want to know more about this subject, click bidding with weak, invitational and game forcing hands with both majors over partner's 1NT.

Un saludo, regards from Barcelona

Answer Peter van der Linden (North)

Dear Jan,

I have given my answer mostly by adding to Ed's text above.
I want to dwell, however, on classical Stayman, since I think Ed was a bit too quick in assuming most pairs play weak Stayman (or whatever name they give it). After that I want to do some summing up and give you a link to Smolen (transfers), a convention that is tightly connected with this piece of bidding theory.
You asked for advice on 5 and 10 HCP hands only. However, Ed (rightly) has reviewed three different strength hands: weak (0-7), invitational (8-9) and game forcing (10⁺), giving a fuller picture.

In classical Stayman, the Stayman-bidder always shows at least 8 HCP, if he makes another bid, . So having agreed upon classical Stayman, responder cannot apply the convention with a weak hand (0-7 HCP) and 5-4 in the majors. This is a major disadvantage of this method (but it allows the partnership to play Smolen, read on).
With a weak hand, responder doesn't have a choice therefore: he gives a transfer to his five-card suit and passes the compulsory bid by the 1NT opener. At worst the partnership plays two in a major 5-2 fit, while it has a 4-4 fit in the other major.

Summing it up.
First: if, responding to Stayman, the 1NT opener shows a four-card major, the rest is a matter of showing him support. Don't forget to add distributional points. If you have applied Stayman, while holding 5-4 and 6 HCP, and partner were to show a four-card in your five-card suit, you can add three points: two for your short suit(s), one for your extra trump. Your hand has thus been promoted from weak to invitational strength.
If over Stayman partner were to show a four-card in your four-card suit, you can add two points.
Since showing support belongs to standard bidding theory, I will not explain this any further.
So we solely discuss partner's 2♦ response.

1. You have 5-4 in the majors and play non-forcing/alternative/weak/crawling Stayman (most common — but this kind of Stayman cannot be combined with Smolen transfers, read on to see why)
a. You are weak (0-7): apply Stayman; over partner's 2♦ response bid two in your major five-card.
b. You have invitational strength (8-9): apply Stayman; over partner's 2♦ response jump to three in your major five-card.
c. You have game-forcing strength (10⁺): transfer to your five-card suit; over partner's compulsory bid, bid your four-card suit — without jumping! (not so if you play Smolen transfers, read on to see why).

2. You have 5-4 in the majors and play classical Stayman
a. You are weak (0-7): transfer to your five-card suit; pass partner's compulsory bid.
Disadvantage: you may miss a 4-4 fit in the other major.
Advantage: after an intervention directly over the 2♣ bid, the 1NT opener can safely respond his four-card major at the three level (playing weak Stayman that would be hazardous, since the Stayman-bidder may have zero points...).
b. You have invitational strength (8-9): apply Stayman; over partner's 2♦ response bid two in your five-card major.
This shows a second advantage of classical Stayman: over partner's 2♦ response you don't need the jump to 3♥/♠. Meaning: the bidding stays lower when responder has invitational strength. So you can reserve that jump for special purposes, of which Smolen (see below) is the most effective.
c. You have game-forcing strength (10⁺): same as 1c.

Compare especially 2b with 1a and 1b. These are situations where non-regular partnerships tend to go astray.

I have already mentioned Smolen. To read about this convention see the last part of my answer to another question, click bidding with weak, invitational and game forcing hands with both majors over partner's 1NT. This is the same link that Ed gave earlier.

To conclude I add one more advantage of Smolen. The following NS-pair does play that convention:

As a consequence:

En hils, regards from Orkanger