A walk-in clinic, also known as a walk-in center, is a medical facility that accepts patients on a walk-in basis and with no appointment required. A number of healthcare service providers fall under the walk-in clinic umbrella including urgent care centers, retail clinics and even many free clinics or community health clinics. Walk-in clinics offer the advantages of being accessible and often inexpensive. It is estimated that there are nearly 11,000 walk-in clinics in America, although it is impossible to calculate an exact number given the variable and ill-defined nature of the category. Urgent care centers make up the largest percentage of walk-in clinics in America with an estimated 9,000 locations nationwide. In fact, consumers often erroneously refer to all walk-in clinics as urgent care centers, and vice versa. Retail clinics are the next most prevalent in the industry with 1,443 locations as of July 1, 2013.