In its latest bid to take on Internet powerhouse Amazon.com Inc. this holiday season, Wal-Mart Stores Inc. is promising same-day delivery in some cities for orders placed online.

Called Wal-Mart To Go, the service costs $10 regardless of the size of the order. The products will be shipped from the company's stores, not from a warehouse or distribution center. Wal-Mart began testing the same-day service last week in Philadelphia and northern Virginia.

It...