Gyula Sax was 1971/72 Junior European champion ( U20) in Groningen ( shared with René Borngässer which had the lower rating ). 1972 FIDE awarded him the title of International Master in 1974 the title of Grand Master. He won tournaments in Rovinj -Zagreb 1975, Vinkovci 1976, Las Palmas in 1978 and Amsterdam in 1979. 1987, he achieved his greatest success when he won the Interzonal in Subotica (divided). In the subsequent cycle candidates he defeated in the second round in 1988 in St. John's, the British Nigel Short with 1.5-3.5 ( 0 = 3, -2). 1990 Sax qualified Interzonal in Manila again for the candidates tournament. There reached in the second round against Viktor Korchnoi, a 4:4 ( 1, = 6, -1), but lost the tie-break in rapid chess.
His last Elo rating was 2439, its highest was 2610 in January 1988 and January 1989. Thus he finished in January 1988 the shared 15th place of the FIDE world ranking list (along with Ljubomir Ljubojević and Lajos Portisch ), in January 1989, together with eight other players split the 12th place.
Gyula Sax took from 1972 to 2000 with the Hungarian national team in ten Chess Olympiads. The greatest success was in this case the profit of the Chess Olympiad in 1978 against the Soviet Union, which had previously occupied the first place in all participants. In this tournament, Sax also reached third place in the individual standings board 3, further he finished at the Chess Olympiads in 1972 and 1980 with the Hungarian team to second place. At the World Team Championships in 1985 and 1989 Sax belonged to the Hungarian selection. 1985 occupied the Hungarian selection second place, Gyula Sax was also the most successful players on board 3 Between 1973 and 1997 Sax adopted six European Team Championships and arrived here two second and third places. In the European Team Championship in 1973, he was also the top scoring player on board 8
In the Hungarian Team Championships, which NB I. Szabó László csoport, Sax played from 2001 until his death in Zalaegerszegi Csuti Antal, with whom he was in 2002, 2003, 2004, 2005, 2006 and 2008 of Hungarian team champion. Before Gyula Sax played at Miskolci SSC and was with this in 2000 and 2001 of Hungarian team champion. In the German Chess Bundesliga Sax played in the seasons 1992/93 and 1993/94 at SC Hagen and in the seasons 1996/97, 1997/98 and 1999/2000 at PSV Duisburg.