Retail clinics, those small health clinics often found in drug and grocery stores, have seen a tremendous increase in patient visits in recent years. In fact, patient visits doubled from 2007 to 2008 and doubled again from 2008 to 2009, according to a new study conducted by the RAND Corporation and published online in Health Affairs. Although visits to retail clinics still make up a small portion of the overall outpatient market, researchers estimated there were nearly 6 million retail clinic visits in 2009 alone