OBJECTIVES: Antibiotic prescribing via telephone may be associated with inappropriate antibiotic use and potential bacterial resistance, although limited data exist regarding this practice. The purpose of this analysis was to examine the prevalence and patterns of telephone antibiotic prescribing. METHODS: Patients’ antibiotic prescription data were retrieved from a large, Mid-Atlantic health system outpatient electronic medical record from 2006-2010. Antibiotic prescriptions were categorized as initiated by telephone or office visit and by antibiotic classifications; antibiotics for chronic use were excluded.  Practices were categorized as teaching or private.  Annual number of patients was calculated as a three-year running average and patient data were censored on date of death, date of last activity plus 24 months, or January 1, 2011, whichever came earliest. Rates of telephone antibiotic prescribing were calculated and stratified by practice type and antibiotic classification.   RESULTS: The analysis included 219,282 patient-years (pt-yrs), during which 64,193 antibiotic prescriptions were generated. Overall antibiotic prescribing was 29.3/100 pt-yrs; 12.4% of the antibiotics were prescribed via telephone, although 39.0% of these “telephone-antibiotic” patients had an office visit in the prior 7 days.  Antibiotic prescribing overall and via telephone was greater in private practices (34.7/100 pt-yrs and 14.0%) compared with teaching practices (20.6/100 pt-yrs and 8.0%) (both P<0.05).  Macrolides (25.4%) and beta-lactams (22.9%) were the most commonly prescribed antibiotic classes overall with macrolides and quinolones most common via telephone.  Approximately one-fifth of quinolone prescriptions (20.1%) were prescribed via telephone, including 16.6% for newer quinolones (levofloxacin or moxifloxacin). CONCLUSIONS: Prescribing via telephone occurred in approximately one in eight antibiotic prescriptions and varied by practice type and antibiotic classification.  Significant numbers of prescriptions for newer, broad spectrum antibiotics were generated telephonically.  The frequency and prescribing patterns associated with telephone antibiotic prescribing in this population support the need for further study of its impact on antibiotic resistance.