Oxygen is a commonly used medication in both inpatients and outpatients. When a team of residents and attending physicians gave different answers as to the oxygen flow rate a patient was receiving while looking at the same oxygen flowmeter above a single patient's bed, the author wondered why the answers varied. Convenience samples of attending physicians, fellows, residents, interns, nurses, and respiratory therapists were surveyed by the author regarding how each provider determined what oxygen flow rate a patient was receiving. Sampling occurred in August and May of the 2003-2004 academic year. After handing in their survey, all respondents were briefly instructed as to which portion of the floating ball in the oxygen flowmeter was to be used to interpret oxygen flow rates according to the manufacturer's literature. Surveys responses were reviewed at a later date. Several trends emerged: Most providers use a variety of techniques to determine the oxygen flow rate a patient is receiving, including review of respiratory therapy notes, “ask the nurse,” and checking the flowmeter on the wall in the patient's room. Respiratory therapists and nurses were more likely than physicians of any level of training to interpret the flowmeter correctly. Only respiratory therapists universally “read the ball” in the middle, as recommended by the flowmeter manufacturer for accurate flow interpretation. The most common error in interpretation by physicians and nurses was to “read the ball” at the bottom. The author discusses potential causes and implications for patient care of this very common misreading of a commonly used medical device.