Sequential antimicrobial therapy (SAT) is arousing keen interest in microbiologists and pharmacists. In an attempt to obtain information from these groups regarding the use of SAT in hospitals, an anonymized postal survey was carried out. A SAT questionnaire was circulated to consultant medical microbiologists, clinical microbiologists, and heads of pharmacy departments within the British Isles. Four hundred and forty-seven microbiologists and pharmacists returned completed questionnaires, giving a response rate of 29%. Just over half of medical microbiologists (MM) and pharmacists (PH) indicated that SAT was used in their institution in respiratory medicine, geriatrics, surgery and, significantly, to a lesser degree in paediatrics. The most common infections treated were pneumonia, bronchitis and wound infection. However, there were significant differences between MM and PH, with MM favouring greater use of SAT in peritonitis (P=0.03), septicaemia (P<0.01), bone infection (P<0.01), pyelonephritis (UTI) (P<0.01), and PH favouring use in bronchitis (P<0.01). The ability to take oral fluids or a recognition of no potential absorption problems were key criteria in the decision process leading to the institution of SAT by MM and PH. Significantly more MM favoured employing criteria such as temperature <38 degrees C (P<0.01), no requirement for high tissue concentrations (P=0.02) and evidence of response to i.v. antimicrobial therapy (P<0.01) than PH. The most frequently "switched" antimicrobials were metronidazole, ciprofloxacin and co-amoxiclav. There were more than five times as many MM reporting the use of clindamycin than PH (P<0.01), whereas nearly twice as many PH cited use of cefuroxime (P<0.01). Of those hospitals not employing SAT, most MM and PH concurred that the commonest reason to institute SAT was financial, followed by convenience to patients and staff. However, more PH than MM indicated that protocols (P<0.01) and a reduction in i.v. complications (P<0.01) were important to them. In promoting SAT, MM and PH felt they had the major role. Significantly, each profession felt that the other had a lesser role to play; MM as judged by the PH (P<0.01) and PH as judged by MM (P<0.01). When promoting SAT, both MM and PH felt that "education for clinicians" followed by regular audit was the best way to ensure implementation. However, significant differences arose with PH regarding nurse education (P<0.01), SAT posters (P=0.02), regular review of patients (P=0.04) and patient's notes SAT stickers (P<0.01) as more important to them than MM. Significantly, less MM than PH (P<0.01) insisted that either the i.v. and PO antimicrobials were identical or were from the same group or class when "switching". This survey highlights interesting comparisons between the approaches of MM and PH towards SAT and may indicate ways in which both groups may work together to bring about change.