To assess the impact of an infection team review of patients receiving antibiotics in six hospitals across the UK and to establish the suitability of these patients for continued care in the community. An evaluation audit tool was used to assess all patients on antibiotic treatment on acute wards on a given day. Clinical and antibiotic use data were collected by an infection team (doctor, nurse and antibiotic pharmacist). Assessments were made of the requirement for continuing antibiotic treatment, route and duration [including intravenous (iv)/oral switch] and of the suitability of the patients for discharge from hospital and their requirement for community support. Of 1356 patients reviewed, 429 (32%) were on systemic antibiotics, comprising 165 (38%) on iv ± oral antibiotics and 264 (62%) on oral antibiotics alone. Ninety-nine (23%) patients (including 26 on iv antibiotics) had their antibiotics stopped immediately on clinical grounds. The other 330 (77%) patients (including 139 on iv antibiotics) needed to continue antibiotics, although 47 (34%) could be switched to oral. Eighty-nine (21%) patients were considered eligible for discharge, comprising 10 who would have required outpatient parenteral antibiotic therapy (OPAT), 55 who were suitable for oral outpatient treatment and 24 who had their antibiotics stopped. Infection team review had a significant impact on antimicrobial use, facilitating iv to oral switch and a reduction in the volume of antibiotic use, possibly reducing the risk of healthcare-associated complications and infections. It identified many patients who could potentially have been managed in the community with appropriate resources, saving 481 bed-days. The health economics are reported in a companion paper.