Dutch Grandmaster (Honorary Grandmaster, 1982). International Arbiter 1960. Deputy Chief Arbiter at the match Karpov-Kasparov in 1985. Chess journalist and columnist at Het Parool. Netherlands Champion in 1965.
Best results: Ebenze 1933, 2nd; Birmingham 1937 and 1939, 1st -2nd; Gijon 1947, 1st-2nd; Beverwijk 1948, 1st; Niemegen 1948, 1st; Madrid 1951, 1st; Tarragona 1954, 1st.
A participant in 12 Olympiads between 1939 and 1968.
Chief Organizer, he was in charge of prestigious tournaments like Amsterdam 1950, Amsterdam 1954 Olympiad) and the Amsterdam Candidates Tournament 1956.