DENVER - Shares of Chipotle Mexican Grill Inc., the restaurant chain owned by McDonald's Corp., more than doubled in price by midday Thursday in their trading debut on the New York Stock Exchange.

The shares in the initial public offering were priced at $22 a share Wednesday evening, but surged $23.10 to $45.10 in midday trading on the NYSE. Ahead of the pricing, the company had increased the expected range by $2.50 to $18 to $20.

Of the nearly 7.9 million shares offered, Chipotle sold 6.01 million shares, and McDonald's sold 1.82 million, the company said Thursday. Chipotle's class A shares are trading on the NYSE under the symbol "CMG".

The Denver-based company best known for its hefty burritos said it expected to earn about $121.4 million in net proceeds which it will use to expand the business and repay debt. McDonald's of Oak Brook, Ill., will retain a majority stake in Chipotle following the stock offering.

The company initially planned to price the stock between $15.50 a share and $17.50 a share and earlier this week raised the range to between $18 a share and $20 a share before settling on $22 a share.

Founded in Denver in 1993, Chipotle (pronounced chi-POAT-lay) made its name by offering meal-sized burritos, tacos and salads. In 1998, McDonald's purchased a stake in the chain, which had 14 Denver-area restaurants at the time.

Today, there are about 480 Chipotle stores across the nation with plans to add 90 locations this year. Founder Steve Ells has remained its chief executive.

Revenue totaled $470.7 million in 2004, a 130 percent increase from 2002. The company said that was largely driven by higher average store sales and by opening 237 stores from 2002 to 2004.

McDonald's also owns Golden, Colo.-based Boston Chicken Inc., which operates the homestyle meat-and-potatoes Boston Market restaurants.