Wal-Mart Stores, the world’s largest retailer, said yesterday that it would begin selling certain generic prescription drugs for $4 in 11 new states, bringing the total to 38 states.

Wal-Mart, which started the $4 generic drug program in Florida in September, said it was now available in Idaho, Ken tucky, Maine, Massachusetts, Nebraska, Oklahoma, Rhode Island, South Carolina, Utah, Washington and West Virginia.

The cut-price drugs are available in 3,009 pharmacies. Wal-Mart has 3,960 United States stores.

Wal-Mart said the list of generics, which includes some 143 compounds, represented more than a quarter of the prescriptions dispensed in its pharmacies.

To date, as new states have been added to the program, 2.1 million more new prescriptions have been filled in those states as compared with the same periods last year.

When Wal-Mart first announced the $4 plan in September, it drove down shares of drugstore chains. The drugstore companies and analysts have said they envision little threat from Wal-Mart’s plan, noting that cash prescriptions account for only a small portion of their profits.