After a barren run lasting 24 years, Hungary are suddenly chasing back-to-back Olympic gold medals in men's waterpolo.

Hungary are the most successful country in Olympic waterpolo but had to wait almost a quarter of a century for their seventh title after winning their sixth in 1976.

They ended their drought in Sydney four years ago and, after winning last year's world championship, the eastern Europeans are favourites to defend their crown in Athens.

Their biggest threat in the 12-nation men's tournament is Serbia and Montenegro, who won consecutive gold medals in 1984 and 1988 competing as Yugoslavia.

They finished third at the world titles and were second to Hungary in this year's World League. Italy also loom as strong contenders after taking silver at the worlds.

The United States are favourites to win the eight-team women's competition after finishing with silver four years ago.

Australia took the gold with a goal 1.3 seconds from time when women's waterpolo was introduced to the Olympics for the first time.

Most of the Australian players who won in Sydney have now retired, leaving Russia and Italy as the main rivals to the Americans.

The men's waterpolo competition starts tomorrow and finishes on August 29, while the women's event commences a day later and runs for 10 days.