Australian Open organisers gave the thumbs-up Monday to spectator behaviour, with no repeat of the ugly ethnic violence which marred the event's opening day last year.
Tournament director Craig Tiley said the only incident of concern was a fan letting off a flare within Melbourne Park, with authorities investigating.
No arrests have been made.
At last year's tournament, Serbian and Croatian fans, wearing the national colours of the bitter Balkan rivals, clashed using flagpoles, bottles and boots, with more than 150 spectators ejected.
There has been a long history of violence between Serb and Croat fans in Melbourne but it had previously been restricted to football matches.
"We're very happy with crowd behaviour. The crowds have been extremely well behaved," Tiley told reporters.
"There was a flare on Heineken Hill, away from people but within 40 seconds our security personnel were at the site and stamped out the flare. At this point we're still investigating."
More than 41,000 spectators attended the day session at Melbourne Park -- a first day record.