Galle - Chris Gayle became the first West Indies batsman to hammer a triple-century in an away Test, putting Sri Lanka under pressure in the opening Test on Tuesday.
The former captain made a career-best 333 as the West Indies posted a massive 580-9 declared in their first innings on the second day at the Galle International Stadium.
Sri Lanka were 54-1 in reply at stumps, with debutant West Indies paceman Andre Russell dismissing Tillakaratne Dilshan with his second delivery in Test cricket.
Skipper Kumar Sangakkara (33) and Tharanga Paranavitana (10) were the not-out batsmen at the close.
Gayle, 31, also became only the fourth batsman to score two triple-centuries in Tests after Australian Don Bradman, India's Virender Sehwag and West Indies' Brian Lara.
"Taking early wickets (on Wednesday) will be the key," said West Indies vice-captain Brendan Nash.
"I think we are on top at the moment. We have a young bowling attack and Sri Lanka are used to scoring big totals, so we'll have to stick to our game plan. I think spin will play a big part.
"It was disappointing to lose wickets in the end, but (Sri Lankan spinner) Ajantha Mendis bowled really well."
Gayle was instrumental in frustrating Sri Lanka for a second successive day with his superb knock, adding 86 for the third wicket with Shivnarine Chanderpaul (32) and 167 for the next with Nash (64).
Gayle, whose previous Test-best was 317 against South Africa at home in 2005, smashed nine sixes and 34 fours in his marathon 437-ball knock.
Batting with a runner due to cramp after achieving his career-best score, Gayle also helped the West Indies post their highest Test total against Sri Lanka, surpassing 477-9 declared in St Lucia in 2003.
Gayle batted for more than five sessions before falling in the evening, bowled by unorthodox spinner Mendis. Sri Lanka's players shook hands with the batsman when he walked back to the dressing-room.
Mendis, who bowled Gayle and new skipper Darren Sammy with successive balls, finished with 6-169 for his third haul of five or more wickets in a Test innings as the West Indies lost their last six wickets for 21 runs in a late collapse.
"I think I bowled with more variations today," said Mendis.
"The pitch is still good for batting, but it is getting slower. (Off-spinner) Suraj Randiv bowled well and we managed to get wickets in the last session after Gayle's dismissal."
Gayle's memorable moment came when he fluently drove Mendis through the covers for a four to reach his triple-century. He then raised his helmet and bat and sat on the pitch in celebration.
He was fortunate to survive on 287 when he was caught by Sangakkara at short extra cover while fending off a rising delivery off seamer Dammika Prasad, but it was ruled a no-ball.
Gayle started walking back to the pavilion before being stopped by non-striker Nash. The decision was referred to the TV umpire before on-field umpire ruled it a no-ball.
Sri Lanka managed to contain runs, but found wickets hard to come by as they could dismiss just one batsman in the first two sessions.
Gayle, who batted aggressively on Monday to score 219 off 247 balls, played cautiously in the morning and added just 36 to his overnight score with the help of three fours.
The West Indies added 67 to their overnight total of 362-2 for the loss of one wicket in the morning.
Chanderpaul fell soon after becoming the world's 10th batsman and the second West Indian after Lara (11,953) to complete 9,000 Test runs during his 104-ball knock.
He was caught by Mahela Jayawardene at first slip while attempting to cut Randiv, adding only 12 to his overnight score 20.
But there was no respite for Sri Lanka as Nash gave valuable support to Gayle with a solid knock, hitting five fours in his seventh Test half-century.