Antibiotics account for a substantial proportion of hospital drug expenditures and tend to be misused or overused, generating unnecessary costs and causing the emergence of resistant bacteria. Antibiotic use was evaluated in a one-day prevalence study performed on the surgical and medical wards of eight Swiss non-university hospitals. 173 of the 695 inpatients present (25%) were on antibiotics and 163 could be evaluated. 35 prescriptions were secondary to an infectious disease consultation. 60 of the remaining 128 (47%) were considered inappropriate, of which 17 (28%) lacked any indication for antibiotic use. The rates of misuse were higher in surgery than in medicine (58 vs. 34%; OR = 2.5 [95% CI: 1.1-5.9]), and higher for prophylaxis than for treatment (72 vs. 41%; OR = 4.1 [95% CI: 1.3-15.5]). Savings of 545 euros (95% CI: from -116 to 1,206 euros) on the study day and 6,256 euros (95% CI: from -2,221 to 14,732 euros) for the total treatments or prophylaxis administered would have resulted from infectious disease consultations.