1964 on 7½/11 behind Arturo Pomar. He shared the title at Beverwijk 1965 on 10½/15 with Geller. At Yerevan 1965, he was fifth with 7/13 as Korchnoi won. With six of the world's top 25 in the field at Zagreb 1965, Portisch scored 12/19 for a shared third/fourth place, as Borislav Ivkov and Uhlmann won. He was third at Mar del Plata 1966 on 9½/15, with Smyslov winning. Portisch shared the title at Kecskemét 1966 on 6½/9, along with Vlastimil Hort. At Santa Monica 1966, with seven of the world's top 16 players in the field, he shared fourth/fifth places on 9½/18, as Spassky won, ahead of Fischer. Portisch was third at Palma de Mallorca 1966 on 10/15, with Tal winning. Portisch won Amsterdam IBM 1967 with 8/11 ahead of Alexander Kotov. At Moscow 1967, which had 12 of the world's top 33 players, he shared sixth/eighth places with 9½/17, and defeated World Champion Petrosian; the tournament winner was Leonid Stein. Portisch placed fourth at Palma de Mallorca 1967, where seven of the top 30 played, with 11½/17; Larsen won. At Wijk aan Zee 1968, he shared second/fourth places with 9/15 as Korchnoi won. Portisch shared sixth/eighth places at Monte Carlo 1968, which had five of the top 16 players; Larsen won. One of Portisch's career highlights was his clear first place at Skopje/Ohrid 1968, ahead of Geller, Lev Polugaevsky, and Hort, with 14/19. The year 1969 was his most successful to date. He won Amsterdam IBM 1969 by 1½ points with 11½/15. At Wijk aan Zee 1969, he shared third/fourth places on 10/15, behind winners Mikhail Botvinnik and Efim Geller. Portisch shared first/second places at Monte Carlo 1969 with Vasily Smyslov on 8/11. Then he took clear first at Hastings 1969–70 with 7/9, ahead of Wolfgang Uhlmann, Vasily Smyslov, and Svetozar Gligorić. At Budapest 1970, he shared fifth/sixth places on 8/15, with Paul Keres winning. Portisch played board three at Belgrade 1970 in the USSR vs Rest of the World match, defeating Viktor Korchnoi by 2½–1½. Portisch won at Hastings 1970–71 with 6/9, ahead of Vlastimil Hort, Svetozar Gligorić, and Wolfgang Uhlmann. At Amsterdam IBM 1971, he shared second/fourth places on 9/15 behind Vasily Smyslov. By 1972, Portisch was a major contender to win any tournament he entered. He won Wijk aan Zee 1972, which had six of the top 25 players, with 10½/15, ahead of Arturo Pomar, Walter