The Perth Saints dominated the first half, but found bottom side Airdrie Utd a tough nut to crack in a disappointing first period.
In the 18th minute Jason Scotland beat the offside trap and charged towards Stephen Robertson's goal. The striker shot straight at Robertson when a square ball to either strike partner Steve Milne or new signing Willie McLaren would surely have opened the scoring.
The title challengers weren't to be denied, though, and took a deserved lead in the 40th minute with Milne scoring from point-blank range after a Paul Sheerin corner was knocked on by Simon Mensing and then Martin Hardie in the box.
Airdrie started the second half in a far more threatening fashion than they had played the entire first half and created their first chance of note, but Stuart Taylor blazed over from a Gary Twigg knock -own.
Hardie should have extended St Johnstone's lead in the 70th minute but fluffed his chance from six yards after he was set up through brilliant flowing play from Scotland and Sheerin.
The game ended 1-0, though, and St. Johnstone were well worth the three points to join Livingston at the top of the league.