Objective: Effective management of asthma requires the development of a partnership between the patient and his or her health care professionals. In a number of countries, including Turkey, pharmacy workers are the last link in the asthma therapy chain and usually give information to their patients about the use of these drugs and asthma. As a result, we investigated knowledge of asthma and the use of inhaler devices in pharmacy workers in Istanbul pharmacies. Methods: The study was performed with 266 pharmacists and 261 pharmacist assistants selected from 4221 pharmacies in Istanbul by random sampling, with a 90% confidence interval. Each patient was asked to fill out a questionnaire that measured their knowledge of asthma. They were also asked to demonstrate how to use the inhaler devices. Results: The high number of incorrect answers to the 11th question, that "the majority of upper respiratory tract infections triggering asthma are viral'', may be a contributor to the unnecessary use of antibiotics in Turkey (incorrect answers from 41.2% of pharmacists and 34.5% of pharmacist assistants). Scores for inhalation device techniques for the pharmacists were as follows: metered-dose inhaler (MDI), 4.9 +/- 3.9; discus, 4.4 +/- 3.7; aerolizer, 4 +/- 3.1; and turbuhaler, 3.8 +/- 2.9. Conclusions: Istanbul pharmacy workers have limited knowledge about asthma and inhaler devices and need further education, which may contribute to improved asthma control in Turkey.