At the 1957 Wageningen Zonal, he tied for 3rd–4th places, along with Jan Hein Donner, with 12½/17; there were only three qualifying berths, so the two players had to dispute a playoff match. Larsen won by 3–1 over Donner at The Hague 1958 to qualify for his first Interzonal, at Portorož 1958. Larsen could score only 8½/20 for 16th place, and was not close to qualifying. But he scored his first major individual international success by winning Mar del Plata 1958 with 12/15, ahead of William Lombardy, Erich Eliskases, Oscar Panno, and Herman Pilnik.