OBJECTIVES: Irrational antibiotic usage is still common in Turkey; and antibiotics are still the most commonly prescribed drugs in Turkey. The aim of this study was to evaluate the effects of generic drug usage in inpatient clinics in Turkey, compared to brand names. METHODS: Data was collected from the inpatient clinic of the Infectious Disease Service of a University Hospital, in 2007. A total of 92 patients were treated during this period, and 73% of them received antibiotics. The name of the antibiotic, dosage and the duration of use were recorded by the researcher from patient records. The price of the antibiotics were extracted from the Ministry of Health's official price list. The cost of the bio-equivalent and the cheapest generic drugs were compared with the original drugs. RESULTS: During 2007, the cost of the antibiotics used at the Infectious Disease inpatient clinic was $39,792.6, compared to the cheapest generics, which would have been $38,396.3. In this clinic, $20.8 per patient more was paid for the brand name antibiotics each month. If the 2000-2200 patients being treated with antibiotics in this hospital per year are considered, an average of $47,484,980.1 per year is being paid for brand name antibiotics. CONCLUSIONS: Considering antibiotics are the most commonly used medication in Turkey (17% of total drug usage), it can easily be understood how the use of Brand Name drugs rather than Generics would lead to a vast economic burden. This shows the importance of promoting the use of generic antibiotics and the need for cost-minimalization analysis.