On December 31, 1930, in need of money, he turned professional and joined the fledgling pro tour, which had begun only in 1927. For the next 15 years, he and a handful of other professionals such as Hans Nüsslein and Karel Koželuh barnstormed across the United States and Europe in a series of one-night stands, with Tilden still the player that people primarily paid to see. Tilden beat Koželuh 50–16 on the 1931 tour. Even with greats such as Ellsworth Vines, Fred Perry, and Don Budge as his opponents, all of them current or recent world no. 1 players, it was often Tilden who ensured the box-office receipts—and who could still hold his own against the much younger players for a first set or even an occasional match. Tilden thought he reached the apogee of his whole career in 1934 at 41 years old; nevertheless, that year he was dominated in the pro ranks by Ellsworth Vines. "American Lawn Tennis" reported that Vines had an edge of 11–9 in the first phase of their tour from January 10 through February 16 and that Vines led Tilden by 19 matches after the second phase of their tour, played from March 21 through May 17. Tilden had won 17 times for the entire year, per an Associated Press report, so a probable win-loss record at tour's end was 36–17 in Vines' favor. Both players then met at least 6 times during the rest of the year (Ray Bowers has listed 5 tournament matches and 1 one-night program), all lost by Tilden. In 1931, Tilden won his first US Pro title, beating Vincent Richards in the final. In 1935 he took his second US Pro title beating Kozeluh in the final. Tilden also won the French Pro title in 1934. By the late 1930s, Tilden was in his mid 40s and past his prime, though he was still capable of playing excellent tennis in patches. Tilden lost easily to Don Budge in the 1941 World Series. Budge said of Tilden "Bill could invariably manage to keep things close for a while. It was seldom, however, that he could extend me to the end, and I swamped him on the whole tour". In 1945, the 52-year-old Tilden and his long-time doubles partner Vinnie Richards won the professional doubles championship—they had won the United States amateur title 27 years earlier in 1918.