Lohse was 15-6 with a 3.78 ERA this season and led the staff with 200 innings. He agreed to a $4.25 million, one-year contract on March 14.
His new deal contract calls for a $1.25 million signing bonus and salaries of $7,125,000 next year, $8,875,000 in 2009 and $11,875,000 in each of the final two seasons. He also gets a full no-trade clause.
Lohse said he was able to remain more consistent this season in part because of better preparation under pitching coach Dave Duncan and manager Tony La Russa.
"I've had pretty good runs in the past but I'd have a couple of games where it skewed the numbers a little bit," he said.
"He really became the glue of what we needed to have happen," general manager John Mozeliak said at a news conference.
St. Louis' pitching depth is uncertain. Chris Carpenter, the 2005 NL Cy Young Award winner, missed nearly all of the past two seasons with injuries. He has been diagnosed with irritation of nerves that feed the muscles in the back of his shoulder.