Inverness failed to score for the first time this season but stretched their unbeaten run to nine games and retained second place in the Clydesdale Bank Premier League.
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Caley Thistle had found the net in their previous 25 matches this season, with their SPL games averaging four goals a game, but they found St Johnstone difficult to break down despite having two one-on-ones in the opening stages, neither straightforward.
Gregory Tade had a similar chance saved for the hosts, who also saw David McCracken's header cleared off the line, but the game lacked the spark associated with Inverness throughout the season.
Caley Thistle last failed to score on May 2, in a draw against Dunfermline which secured their SPL status, and McDiarmid Park was the last away venue they failed to find the net at, in another goalless encounter on April 7.
The chances of another one seemed slim in the opening stages. SPL top goalscorer Billy McKay had the opportunity to add to his tally in the second minute when he got the better of Frazer Wright on the left wing and bore down on goal but the angle proved too tight and he curled just beyond the far post.
McKay's lay-off soon set up Andrew Shinnie to run through on goal after nutmegging Wright. The Scotland international got past another defender but Alan Mannus was quickly off his line and blocked the shot with his legs.
The 10th minute saw widespread applause in a planned tribute for former Motherwell captain Phil O'Donnell, who died five years ago on Saturday after collapsing during a game against Dundee United.
St Johnstone's first effort on goal came from Liam Craig's powerful free-kick from 30 yards but it was straight at Antonio Reguero, who punched away.
Craig set up another chance with a dangerous inswinging corner but both Tade and McCracken just failed to make contact in the six-yard box.
The hosts were dominating possession and Inverness defender Gary Warren twice headed clear well from dangerous crosses.
Saints came close in the 41st minute when McCracken met Craig's deep corner but Owain Tudur Jones headed off the line.
Patrick Cregg was soon booked for diving in the visitors' box and Caley Thistle almost snatched a half-time lead when McKay's flick set up Aaron Doran, whose angled left-footed shot was stopped by the diving Alan Mannus.
The second half saw plenty of effort from both teams going forward but little cutting edge.
Saints changed their strikeforce in the 59th minute when Rowan Vine replaced Steven MacLean and the substitute soon played Tade through but the former Inverness forward could not steer his shot past Reguero, who blocked with his feet.
Tade almost made amends with a persistent run at the heart of the visiting defence that allowed Dave Mackay a strike at goal with Reguero stranded, but Warren was quickly out to block and Murray Davidson headed wide after Craig returned the ball into the box.
Ross Draper forced a chance at the other end when he won the ball just outside the box and kept moving forward but Mannus was quickly off his line to block.
Conor Pepper and Philip Roberts came on for Inverness and the latter's header from a corner was flicked just over by McKay.
But the on-loan Arsenal forward squandered a great chance to play Tudur Jones clear on the counter-attack as he delayed and then under-hit his pass.
Inverness brought on Nick Ross for his comeback from a shoulder injury but there were no late chances.