[3][4][5] He reached his first Grand Slam final at the U.S. championships in 1950, beating Bill Talbert and Gardnar Mulloy and then losing to Art Larsen.

[9] That year, he was ranked number 4 in the U.S.[7] In 1952 at Wimbledon, Flam beat Mulloy and Vic Seixas and then lost in the semifinals to Jaroslav Drobny.

[9] That year, he was ranked number 5 in the U.S.[7] In the 1956 Australian Championships, Flam beat Ashley Cooper and then lost in the semifinals to Ken Rosewall.

[10][11] In September 1956 Flam won the singles title at the Pacific Southwest Championships, defeating Rosewall in the final in five sets.

[12] That year, he was ranked number 2 in the U.S.[7] At the 1957 French championships Flam beat Mervyn Rose in a five-set semifinal and then lost in straight sets to Sven Davidson in the final.