Stoltz played a few matches with strong chess masters. In 1926, he lost to Mikhail Botvinnik at a team match Stockholm – Leningrad in Stockholm. In 1927, he drew with Allan Nilsson in Göteborg. In 1930, he won against Isaac Kashdan in Stockholm. In 1930, he lost to Rudolf Spielmann in Stockholm. In 1931, he won against Salo Flohr in Göteborg. In 1931, he lost to Flohr in Prague. In 1931, he drew with Gideon Ståhlberg in Göteborg. In 1934, he lost to Aron Nimzowitsch in Stockholm. In September 1935, he played at a match Sweden vs Germany, and took 2nd individual result, behind Ståhlberg, in Zoppot. Stoltz played for Sweden in nine Chess Olympiads and in 3rd unofficial Chess Olympiad at Munich 1936:
at fourth board in the 1st Olympiad at London 1927;
at third board at the 11th Olympiad at Amsterdam 1954.
At the beginning of his international career, Stoltz tied for 11-13th in Berlin in 1928. The event was won by Efim Bogoljubow. In 1930, he tied for 2nd-3rd with Bogoljubow, behind Kashdan, in Stockholm. In 1931, he tied for 4-7th in Bled. In 1931/32, he tied for 5-8th in Hastings. In 1932, he won in Swinemünde. In 1933, he took 2nd, behind Nimzowitsch, in Copenhagen. In 1934, he took 3rd in Stockholm. In 1935, he tied for 1st with Lindberg in Harnosand. In 1935, he took 4th in Örebro. In 1935, he tied for 5-6th in Bad Nauheim. In 1936, he tied for 2nd-3rd with Böök, behind Vladimirs Petrovs in Helsinki. In 1936, he took 3rd in Helsinki. In 1937, he tied for 3rd-4th in Stockholm. In 1938, he won in Stockholm. In 1939, he took 5th in Stockholm. During World War II, Stoltz played in Sweden and Germany. In 1940, he tied for 4-5th in the Stockholm championship, which was won by Nils Bergqvist). In September 1941, he won, ahead of Lundin and Alekhine, in the Munich 1941 chess tournament. In June 1942, he took 6th in the Salzburg 1942 chess tournament. In September 1942, he tied for 9-10th in Munich. The event was won by Alexander Alekhine. In 1943, he tied for 1st with Lundholm in Stockholm. In 1943/44, he took 4 th in Stockholm. In 1944, he took 3rd, behind Stig Lundholm, and Paul Keres, in Lidköping,. After the war, Stoltz played in a few international tournaments. In 1946, he took 2nd, behind Albéric O'Kelly de Galway in Beverwijk. In 1946, he took 4th in Zaandam. In 1946, he tied for 8-9th in the Groningen 1946 chess tournament. In 1946, he tied for 2nd-3rd in Prague. In 1947, he tied for 1st with Eero Böök in Helsinki, and drew a play-off match. In 1948, he took 18th in Saltsjöbaden. The event was won by David Bronstein. In 1948, he won in Stockholm. In 1948, he tied for 4-5th in Karlovy Vary – Mariánské Lázně. The event was won by Jan Foltys. In 1950, he tied for 9-13th in Bled. In 1951, he tied for 8-9th in Dortmund. In 1951, he tied for 3rd-4th in Mariánské Lázně – Prague. In 1962, he took 12th in Belgrade. Stoltz won the Swedish championships at Halmstad 1951, Hålland 1952, and Örebro 1953. He was awarded the International Master title in 1950, and the Grandmaster title in 1954.
