BACKGROUND/AIMS: The aim of this study was to investigate antimicrobial use during periodontal therapy in dental practice in England & Wales. METHOD: This was a postal questionnaire survey of 800 dentists, 400 general dental practitioners (GDP) in National Health Service practice and 400 members of the British Society of Periodontology (Periodontal Society) primarily in dental practice. We designed and piloted a questionnaire to evaluate both systemic and local antibiotic use with periodontal therapy as well as factors affecting their prescription. In addition, we also investigated the potential use of antibiotic sensitivity testing, since this has been recommended prior to prescribing antibiotics. Two follow-up mailings were used to encourage non-responders. RESULTS: The useable return rate for the questionnaires was 587/800 (73%). Systemic antibiotics were used by 7.4% Periodontal Society members and 18.4% GDP for untreated adult periodontitis patients (p<0.001). Antimicrobials were prescribed more frequently by Periodontal Society members in early onset (52.7%) and refractory periodontitis patients (49.6%), and this was highly statistically significantly greater usage than GDP (p<0.001). Regarding local antimicrobials, usage for untreated adult periodontitis was Periodontal Society 8.9% and GDP 5.4%. Higher usage of local antimicrobials was found both for the treatment of recurrent pocketing in adult periodontitis (Periodontal Society 26.3%, GDP 14.8%, p<0.014) and refractory periodontitis (Periodontal Society 30.8%, GDP 15.2%, p<0.001). As reasons for using local antimicrobials, more than 80% of all respondents stated superiority over root debridement alone. Barriers to use included cost, no perceived need and lack of supporting research data. The percentage of responders considering diagnostic microbiology either theoretically or at a cost of pound 60 were by group, Periodontal Society 83% & 70.4% and GDP 76% & 51.2%. 33% of Periodontal Society members and 3.8% of GDP spent at least 45 min per quadrant on root planing and Periodontal Society members had a greater exposure to lectures on both systemic and local drug therapy compared with GDP (p<0.001). CONCLUSIONS: Systemic antimicrobial use was infrequent for adult periodontitis and generally in line with current recommendations for other disease types. Whilst local antimicrobial therapy for periodontitis was not widespread, a substantial minority of dentists use this form of therapy and most believe that it is more effective than root debridement alone.