Inappropriate prescribing of antibiotics by health care professionals is a worldwide concern. This study evaluated the knowledge and practices of dental practitioners in the city of Shiraz, Islamic Republic of Iran regarding their therapeutic use of antibiotics for patients with dentoalveolar infections. Of 219 (48.6%) dentists responding to the questionnaire more than 40% would prescribe antibiotics for localized fluctuant swelling and for problems for which antibiotics are not required according to good practice guidelines (acute pulpitis, chronic apical infection, periodontal abscess, chronic gingivitis, chronic periodontitis, pericoronitis and dry socket). A majority correctly prescribed antibiotics for acute periapical infection (77.2%), cellulitis (75.3%) and acute ulcerated gingivitis (63.0%). Amoxicillin was the most frequently prescribed antibiotic for all clinical conditions but there was a wide variation in dosage, frequency and duration for all antibiotics used. Guidelines on rational antibiotic use are needed for dental practitioners in the Islamic Republic of Iran.