Purchasing prescription drugs in a three-month supply rather than a one-month supply has long been regarded as a way to reduce the cost of drugs for patients and third-party payers. New research from the University of Chicago quantifies the savings for the first time. An analysis of 26,852 prescriptions filled for 395 different drugs from 2000-2005 showed that patients who purchased their drugs in three-month supplies rather than with one-month supplies saved on average 29% in out-of-pocket costs. After factoring in third-party payers, including Medicare, Medicaid and insurance companies, total savings averaged 18%.