A seven-time world champion, her most recent win is the McConnell Cup in Orlando, FL, Karen is perhaps best known for her aggressive and complex "light initial action" bidding system. Although the five-card (non-vul) "McCallum weak 2-bids" (with no restrictions on suit quality or side holdings) are no longer an oddity among experts, Karen saw their promise in the 1970s.

Respected around the world as a bidding theorist as well as a player, Karen has served as a coach of several Turkish national bridge teams (open, women, and junior), and of the Australian open national bridge team. She was the NPC for the Turkish juniors in the 2000 Junior World Championships in Antalya. Karen has been an invited participant in bidding panels in numerous bridge publications in England, Australia, Turkey, New Zealand, France and the US. She has also edited several bridge books, including the best-selling bridge book of all time, Larry Cohen's "To Bid or Not to Bid."

In addition to her great success in women's bridge, Karen has had some memorable experiences in open bridge. She was invited (with her partner, Kerri Sanborn) to play in the 1990 Rosenblum Teams with Peter Pender, Ralph Cohen, Bob Jones, and Mike Smolen, and the team faced a formidable opponent in the round of 16: Bob Hamman, Bobby Wolff, Chip Martel, Lew Stansby, Jimmy Cayne, and Chuck Burger. At the half, Pender's team was down 15 IMPs, and one team member suggested that perhaps "the four guys" should play the rest of the way. But Pender sent in McCallum and Sanborn for the second half and won the match. Pender's team eventually lost in the round of 8 to the German open team that won the event.

A woman of many talents and interests, Karen's primary work outside bridge is creating hand-crafted glass and beaded jewelry. You can see examples of Karen's stunning work at www.eclectica3.com. She is an insatiable reader of all genres, with a home library of more than 50,000 volumes. She also enjoys gourmet cooking and playing the piano. She lives in a 215-year-old farmhouse in Exeter, New Hampshire.