Smolen Transfers

The basic idea of Smolen is to get strong 1 NT opener to declare opposite responder 5-4 or 4-5 in the majors by having responder Stayman and then bid the 4 card major. Some use Smolen at both the 2 and 3 levels, but most here in Dallas only use Smolen at the 3 level and leave 2 level bids natural. This is probably best because invitational 5-4 hands are rare compared with weak 5-4 hands due to the narrow HPC range. Briefly:
1NT-2C-2D-2H invitational with 5 spades, 4 hearts
1NT-2C-2D-2S invitational with 4 spades, 5 hearts
1NT-2C-2D-3H forcing with 5 spades, 4 hearts
1NT-2C-2D-3S forcing with 5 hearts, 4 spades

Smolen can also be used with 6-4 or even 7-4 if you and your partner care to work it out.