First baseman Enos Cabell's error with two out in the 19th inning allowed the tie-breaking run to score, and Mike Fitzgerald's single scored two more runs as the Montreal Expos took a 6-3 victory over the Astros last night in Houston.

The game matched the longest in the majors this season, coming three days after the Mets played 19 innings against the Braves in Atlanta.

Montreal catcher Sal Butera was the only nonpitcher not used in the 5-hour 12-minute game.

Singles by Vance Law and Andre Dawson and a fly ball put runners on first and third in Montreal's 19th. With two out, Al Newman bunted to third baseman Denny Walling, but Cabell dropped the throw. Law scored.

A walk to Mitchell Webster loaded the bases and Fitzgerald singled to right for his fourth RBI, scoring Dawson and Newman.

Floyd Youmans (1-0) pitched the last three innings for his first major-league victory. Ron Mathis (3-4) was the loser.

The Expos took a 3-2 lead in the 18th when Terry Francona's single scored Newman, who had doubled, from second base. But Youmans couldn't hold the lead.

Cabell walked and went to third on Mark Bailey's single. When Craig Reynolds grounded to second, Cabell was out in a rundown. Bailey took second. After a strikeout, Bill Doran singled. Bailey scored, but Reynolds was out in another rundown, between second and third.