Last year, I wrote about the new discounted generic drug program introduced by Wal-Mart. The original program provided $4 prescriptions for a 30-day supply of about 300 drugs. At the time, Wal-Mart had tested the program in Florida and then expanded it nationwide. Other national drugstore chains and regional grocery store chains responded by offering their own discounted drug programs. Some retailers, such as Meijer and Publix, began offering free prescriptions for selected drugs. The winners of this pricing competition were the shoppers who took advantage of these programs.

Although Wal-Mart pharmacies would automatically extend the $4 prescription price to any qualifying prescription, many competing pharmacies would only extend the price if the customer knew to ask for a price match. I am sure that many customers did not know that their pharmacies had price matching available, and they most likely paid more than they needed to for qualifying prescriptions. It pays to ask your pharmacy what their generic drug policy is.

Critics of Wal-Mart's program pointed out that many of the drugs on the list were not commonly used, or they were available in a form that was not commonly used. However, Wal-Mart reports that even though the original list of drugs was limited to about 300 generic choices, the original version of the program saved consumers $610 million in prescription costs in its first year. I believe that number is actually higher if we consider the additional savings realized by shoppers who took advantage of competitors' pricing responses.

There are two improvements to Wal-Mart's second phase (Phase 2) of their program. First, the expanded list of participating drugs in Phase 2 includes drugs for glaucoma, attention deficit disorders, fungal infections and acne. Fertility and prescription birth control will also be included at $9, compared to national average prices ranging from $24 to $30 per month, according to Wal-Mart.

The second improvement to Phase 2 reported by Wal-Mart's Web site is that consumers will realize faster savings on new-to-market generics. For example, one month ago, the antifungal "Lamisil had an average price of $337.26. The generic equivalent, terbinafine, is now available through Wal-Mart and Sam's Club pharmacies for $4 for a 30-day supply, saving customers $333.26 per prescription. Carvedilol, the generic for Coreg, which a month ago cost $119, will now cost $4 for a 30-day supply, saving customers $115 per month, or approximately $1,300 per year."

I suggest shoppers pay close attention to their own pharmacies' responses to Wal-Mart's expanded program. We may see other stores match Wal-Mart's improvements, or we may see even more attractive discounts offered by competing pharmacies. The key is to be familiar with your pharmacy's policies or to consider switching to Wal-Mart or Sam's Club pharmacies if you have prescriptions covered by Wal-Mart's program. If you see that you'll be able to save hundreds of dollars a year on one prescription, it may be worth taking the time to transfer your prescription.

To find out more about your specific drug coverage by Wal-Mart's new program, you can read more details at www.walmart.com in the pharmacy section of the Web site. You can also call or visit your local Wal-Mart pharmacy to ask questions in person.

Stephanie Nelson shares her savings tips as a regular contributor on ABC News' "Good Morning America." You can find more of her savings tips in her book "The Greatest Secrets of the Coupon Mom" and on her Web site at www.couponmom.com. She can be reached at shoppingmom@unitedmedia.com.