Walgreens announced Monday that it has extended its agreement to fill prescriptions for customers with prescription drug benefits managed by CVS Caremark. The terms of the agreement were not publicly disclosed.

Walgreens is the nation's largest drugstore chain, with sales of $72 billion in the 2012 fiscal year. CVS Caremark is one of the nation's largest pharmacy benefit management businesses and runs the nation's second largest drugstore chain.

The two companies' multi-year agreement means a continued convenience for customers of both Walgreens and CVS Caremark. The deal could also help to drive drug prices down.

"We are pleased to have reached a mutual, multi-year agreement that meets our business objectives, remains consistent with our principles of receiving predictable and fair reimbursement for the services and value we provide and helps drive cost-effective pricing for payers and patients," said Kermit Crawford, Walgreens president of pharmacy, health and wellness.