-By Eric Newman

McDonald's announced today that its domestic sales grew 4.3% at comp stores in May. The leading restaurant chain attributed the growth to the success of its breakfast menu, as well as recent menu launches like the Southern Chicken biscuit and sandwich.

The company also said its "everyday affordability" message helped drive customers to McDonald's restaurants.

"We're committed to providing our customers with compelling value, unique menu variety and unparalleled convenience," said CEO Jim Skinner, in a statement. "Our steadfast focus on the customer experience . . . continues to deliver positive results worldwide."

But despite an increase in sales, McDonald's growth rate has slowed. According to NPD Group senior industry analyst Marshal Cohen, when consumers need to tighten their budgets, dining out is the first to go. Last May, McDonald's posted comp store sales growth of 7.4%. Overall, the fast-food chain posted 7.7% growth across its 31,000 restaurants worldwide this May, compared to 8.7% in 2007.

Still, McDonald's is experiencing healthy growth, said Ron Paul, president of food industry research firm Technomic, Chicago. At an estimated $29 billion in annual sales, McDonald's is more than three times that of No. 2 Burger King, Paul said.

"They're becoming their own hardest example to follow. Let's give them credit for a good month in light of what's going on in the industry," said Paul. "Their innovativeness with the menu and putting the marketing muscle behind it is part of their formula that's really working for them.